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Prenatal development () includes the development of the embryo and of the
foetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism tha ...

foetus
during a viviparous animal's
gestation Gestation is the period of development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking#Development, Filmmaking, development phase, including finance and budgeting *Development ...
. Prenatal development starts with
fertilization Fertilisation or fertilization (see American and British English spelling differences#-ise.2C -ize .28-isation.2C -ization.29, spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes ...

fertilization
, in the germinal stage of embryonic development, and continues in fetal development until
birth Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the fe ...

birth
. In
human Humans (''Homo sapiens'') are the most abundant and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A speci ...

human
pregnancy Pregnancy, also known as gestation, is the time during which one or more offspring In biology, offspring are the young creation of living organisms, produced either by a Asexual reproduction, single organism or, in the case of sexual repr ...

pregnancy
, prenatal development is also called antenatal development. The development of the human embryo follows
fertilization Fertilisation or fertilization (see American and British English spelling differences#-ise.2C -ize .28-isation.2C -ization.29, spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes ...

fertilization
, and continues as
fetal development Prenatal development () includes the development of the embryo and of the foetus during a viviparous animal's gestationGestation is the period of development during the carrying of an embryo An embryo is the early stage of development of a ...
. By the end of the tenth week of
gestational age Gestational age is a measure of the age of a pregnancy Pregnancy, also known as gestation, is the time during which one or more offspring In biology, offspring are the young creation of living organisms, produced either by a Asexual repr ...
the
embryo An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms ar ...

embryo
has acquired its basic form and is referred to as a
fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism tha ...

fetus
. The next period is that of fetal development where many organs become fully developed. This fetal period is described both topically (by organ) and chronologically (by time) with major occurrences being listed by gestational age. The very early stages of
embryonic development An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms ar ...
are the same in all
mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be i ...
s. Later stages of development across all
taxa In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
of animals and the length of gestation vary.


Terminology

In the human: Different terms are used to describe prenatal development, meaning development before birth. A term with the same meaning is the "antepartum" (from Latin ''ante'' "before" and ''parere'' "to give birth") Sometimes "antepartum" is however used to denote the period between the 24th/26th week of
gestation Gestation is the period of development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking#Development, Filmmaking, development phase, including finance and budgeting *Development ...
al age until birth, for example in antepartum hemorrhage.patient.info » PatientPlus » Antepartum Haemorrhage
Last Updated: 5 May 2009
The perinatal period (from Greek ''peri'', "about, around" and Latin ''nasci'' "to be born") is "around the time of
birth Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the f ...

birth
". In
developed countries A developed country (or industrialized country, high-income country, more economically developed country (MEDC), advanced country) is a sovereign state A sovereign state is a political entity that is represented by one centralized governmen ...
and at facilities where expert neonatal care is available, it is considered from 22 completed weeks (usually about 154 days) of
gestation Gestation is the period of development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking#Development, Filmmaking, development phase, including finance and budgeting *Development ...
(the time when
birth weight Birth weight is the body weight Human body weight refers to a person's mass or weight. Body weight is measured in kilogram The kilogram (also kilogramme) is the base unit of mass in the International System of Units (SI), the current metri ...
is normally 500 g) to 7 completed days after birth. In many of the
developing countries A developing country is a sovereign state with a less developed Industrial sector, industrial base and a low Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no ...
the starting point of this period is considered 28 completed weeks of gestation (or weight more than 1000 g).


Fertilization

Fertilization Fertilisation or fertilization (see American and British English spelling differences#-ise.2C -ize .28-isation.2C -ization.29, spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes ...

Fertilization
marks the first germinal stage of
embryonic development An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms ar ...
. When
semen Semen, also known as seminal fluid, is an organic fluid created to contain spermatozoon, spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphrodite, hermaphroditic animals and can fertilization, f ...

semen
is released into the
vagina In mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian female, femal ...

vagina
, the
spermatozoa A spermatozoon (pronounced , alternate spelling spermatozoön; plural spermatozoa; from grc, σπέρμα ("seed") and grc, ζῷον ("living being")) is a motile Motility is the ability of an organism In biology, an organism () ...

spermatozoa
travel through the
cervix The cervix or cervix uteri (Latin, 'neck of the uterus') is the lower part of the uterus The uterus (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. L ...

cervix
and body of the
uterus The uterus (from Latin "uterus", plural ''uteri'') or womb () is the main female hormone-responsive, sex organ, secondary sex organ of the reproductive system in humans and most other mammals. Things occurring in the uterus are described with t ...

uterus
and into the
fallopian tube The Fallopian tubes, also known as uterine tubes, salpinges (singular salpinx), or oviducts, are tubes that stretch from the ovaries The ovary is an organ found in the female reproductive system 400px, 1. Labia_majora.html"_;"title="V ...

fallopian tube
s where fertilization usually takes place. Many sperm cells are released with the possibility of just one managing to adhere to and enter the thick
protective layer surrounding the egg cell
protective layer surrounding the egg cell
(ovum). The first sperm cell to successfully penetrate the egg cell donates its
genetic material Nucleic acids are biopolymer Biopolymers are natural polymer A polymer (; Greek ''poly- Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much", may refer to: Businesses * China Poly Group Corporation, a Chinese busin ...
(
DNA Deoxyribonucleic acid (; DNA) is a molecule A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically Electricity is the set of physical ...

DNA
) to combine with the DNA of the egg cell resulting in a new organism called the
zygote A zygote (, ) is a eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are ...

zygote
. The term "conception" refers variably to either fertilization or to formation of the
conceptus A conceptus (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman ...

conceptus
after its
implantation Implantation may refer to: * Implantation (human embryo), in which the human embryo adheres to the wall of the uterus * Implant (medicine), insertion of implants * Endometrial transplantation, as part of the Endometriosis, theory of retrograde mens ...
in the uterus, and this terminology is controversial. The zygote will develop into a male if the egg is fertilized by a sperm that carries a
Y chromosome The Y chromosome is one of two sex chromosome A chromosome is a long DNA molecule with part or all of the genome, genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called histones which, aided by Chaper ...
, or a female if the sperm carries an
X chromosome The X chromosome is one of the two sex-determining chromosome A chromosome is a long DNA molecule with part or all of the genome, genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called histones whic ...

X chromosome
. The Y chromosome contains a gene,
SRY Testis-determining factor (TDF), also known as sex-determining region Y (SRY) protein, is a DNA-binding protein protein complex with DNA s (blue). These proteins' basic amino acids bind to the acidic phosphate groups on DNA. repressor heli ...
, which will switch on
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 c ...
production at a later stage leading to the development of a
male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot sexual reproduction, reproduce sexually ...

male
body type. In contrast, the
mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five car ...

mitochondrial DNA
of the zygote comes entirely from the egg cell.


Development of the embryo

Following fertilization, the embryonic stage of development continues until the end of the 10th week (
gestational age Gestational age is a measure of the age of a pregnancy Pregnancy, also known as gestation, is the time during which one or more offspring In biology, offspring are the young creation of living organisms, produced either by a Asexual repr ...
) (8th week fertilization age). The first two weeks from fertilization is also referred to as the germinal stage or preembryonic stage. The
zygote A zygote (, ) is a eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are ...

zygote
spends the next few days traveling down the
fallopian tube The Fallopian tubes, also known as uterine tubes, salpinges (singular salpinx), or oviducts, are tubes that stretch from the ovaries The ovary is an organ found in the female reproductive system 400px, 1. Labia_majora.html"_;"title="V ...

fallopian tube
dividing several times to form a ball of cells called a
morula A morula (Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman R ...
. Further
cellular division Cell division is the process by which a parent cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious ...
is accompanied by the formation of a small cavity between the cells. This stage is called a
blastocyst The blastocyst is a structure formed in the early development of mammal Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in th ...

blastocyst
. Up to this point there is no growth in the overall size of the embryo, as it is confined within a glycoprotein shell, known as the
zona pellucida The zona pellucida (plural zonae pellucidae, also egg coat or pellucid zone) is a glycoprotein Glycoproteins are protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions ...

zona pellucida
. Instead, each division produces successively smaller cells. The
blastocyst The blastocyst is a structure formed in the early development of mammal Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in th ...

blastocyst
reaches the
uterus The uterus (from Latin "uterus", plural ''uteri'') or womb () is the main female hormone-responsive, sex organ, secondary sex organ of the reproductive system in humans and most other mammals. Things occurring in the uterus are described with t ...

uterus
at roughly the fifth day after fertilization. It is here that lysis of the zona pellucida occurs. This process is analogous to
zona hatchingZona hatching is a phenomenon occurring during prenatal development Prenatal development () includes the development of the embryo and of the foetus during a viviparous animal's gestation. Prenatal development starts with fertilization , in th ...
, a term that refers to the emergence of the blastocyst from the zona pellucida, when incubated
in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies Study or studies may refer to: General * Education **Higher education * Clinical trial * Experiment * Observational study * Research * Study skills, abilities and approaches applie ...

in vitro
. This allows the
trophectoderm Trophoblasts (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 mil ...
cells of the blastocyst to come into contact with, and adhere to, the
endometrial
endometrial
cells of the uterus. The trophectoderm will eventually give rise to extra-embryonic structures, such as the
placenta The placenta is a temporary fetal organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. ...

placenta
and the membranes. The embryo becomes embedded in the endometrium in a process called
implantation Implantation may refer to: * Implantation (human embryo), in which the human embryo adheres to the wall of the uterus * Implant (medicine), insertion of implants * Endometrial transplantation, as part of the Endometriosis, theory of retrograde mens ...
. In most successful pregnancies, the embryo implants 8 to 10 days after ovulation. The embryo, the extra-embryonic membranes, and the placenta are collectively referred to as a conceptus, or the "products of conception". Rapid growth occurs and the embryo's main features begin to take form. This process is called
differentiation Differentiation may refer to: Business * Differentiation (economics), the process of making a product different from other similar products * Product differentiation, in marketing * Differentiated service, a service that varies with the identity o ...
, which produces the varied cell types (such as blood cells, kidney cells, and nerve cells). A spontaneous abortion, or
miscarriage Miscarriage, also known in medical terms as a spontaneous abortion and pregnancy loss, is the natural loss of an embryo An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism ...
, in the first trimester of pregnancy is usually due to major genetic mistakes or abnormalities in the developing embryo. During this critical period (most of the
first trimester Pregnancy, also known as gestation, is the time during which one or more offspring In biology, offspring are the young born of living organism, organisms, produced either by a single organism or, in the case of sexual reproduction, two orga ...
), the developing embryo is also susceptible to toxic exposures, such as: *
Alcohol In chemistry, alcohol is an organic compound that carries at least one hydroxyl functional group (−OH) bound to a Saturated and unsaturated compounds, saturated carbon atom. The term alcohol originally referred to the primary alcohol ethan ...

Alcohol
, certain
drug A drug is any chemical substance that causes a change in an organism's physiology or psychology when consumed. Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via insuffl ...
s, and other
toxins A toxin is a harmful substance produced within living cells or organisms; synthetic toxicants created by artificial processes are thus excluded. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived from the word toxi ...
that cause
birth defect A birth defect, also known as a congenital disorder, is a condition present at birth Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiat ...
s, such as
fetal alcohol syndrome Fetal alcohol spectrum disorders (FASDs) are a group of conditions that can occur in a person whose mother drank alcohol In chemistry, alcohol is an organic compound that carries at least one hydroxyl functional group (−OH) bound to ...

fetal alcohol syndrome
*
Infection An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host A host is a person responsible for guests at an event or for providing hospitality during it. Host may ...

Infection
(such as
rubella Rubella, also known as German measles or three-day measles, is an infection An infection is the invasion of an organism's body by , their multiplication, and the reaction of tissues to the infectious agents and the s they produce. An inf ...

rubella
or
cytomegalovirus ''Cytomegalovirus'' (''CMV'') (from ''cyto-'' 'cell' via Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. I ...
) *
Radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and f ...

Radiation
from
x-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Moti ...

x-ray
s or
radiation therapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation Ionizing radiation (or ionising radiation), including nuclear radiation, consists of s or s that have sufficient to s or s by detachi ...

radiation therapy
*
Nutritional deficiencies Malnutrition is a condition that results from eating a diet which does not supply a healthy amount of one or more nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient in ...
such as lack of
folate Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and ...
which contributes to
spina bifida Spina bifida (Latin for "split spine"; SB) is a in which there is incomplete closing of the and the around the during . There are three main types: spina bifida occulta, meningocele and myelomeningocele. Meningocele and myelomeningocele may ...


Nutrition

The embryo passes through 3 phases of acquisition of nutrition from the mother:Daftary, Shirish; Chakravarti, Sudip (2011). Manual of Obstetrics, 3rd Edition. Elsevier. pp. 1–16. . # ''Absorption phase:'' Zygote is nourished by cellular cytoplasm and secretions in fallopian tubes and uterine cavity. # ''Histoplasmic transfer:'' After nidation and before establishment of uteroplacental circulation, embryonic nutrition is derived from decidual cells and maternal blood pools that open up as a result of eroding activity of
trophoblasts Trophoblasts (from Greek 'trephein': to feed; and 'blastos': germinator) are cells that form the outer layer of a blastocyst, and are present four days post-fertilization in humans. They provide nutrients to the embryo An embryo is the early ...
. # ''Hematotrophic phase:'' After third week of gestation, substances are transported passively via intervillous space.


Development of the fetus

Fetal development is the third of the three stages of prenatal development, following from the initial
germinal stage Human embryonic development, or human embryogenesis, refers to the development and formation of the human embryo. It is characterised by the processes of cell division and cellular differentiation of the embryo that occurs during the early sta ...
(preembryonic stage), and stage of
embryonic development An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms ar ...

embryonic development
. These stages are also referred to in
pregnancy Pregnancy, also known as gestation, is the time during which one or more offspring In biology, offspring are the young creation of living organisms, produced either by a Asexual reproduction, single organism or, in the case of sexual repr ...

pregnancy
as terms or trimesters. From the 10th week of gestation (8th week of development), the developing organism is called a fetus. All major structures are already formed in the fetus, but they continue to grow and develop. Since the precursors of all the major organs are created by this time, the fetal period is described both by organ and by a list of changes by weeks of gestational age. Because the precursors of the organs are now formed, the fetus is not as sensitive to damage from environmental exposure as the embryo was. Instead, toxic exposure often causes physiological abnormalities or minor congenital malformation.


Development of organ systems

Development continues throughout the life of the fetus and through into life after birth. Significant changes occur to many systems in the period after birth as they adapt to life outside the uterus.


Fetal blood

Hematopoiesis Haematopoiesis (, from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is a ...
first takes place in the
yolk sac The yolk sac is a membranous wikt:sac, sac attached to an embryo, formed by cells of the hypoblast adjacent to the embryonic disk. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac'' is far ...
. The function is transferred to the
liver The liver is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's t ...

liver
by the 10th week of gestation and to the
spleen The spleen is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's ...

spleen
and
bone marrow Bone marrow is a semi-solid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphos ...
beyond that. The total blood volume is about 125 ml/kg of fetal body weight near term.


Red blood cells

Megaloblastic red blood cells are produced early in development, which become normoblastic near term. Life span of prenatal RBCs is 80 days. Rh antigen appears at about 40 days of gestation.


White blood cells

The fetus starts producing
leukocytes White blood cells (WBCs), also called leukocytes or leucocytes, are the cells of the immune system The immune system is a network of biological processes that protects an organism In biology, an organism (from Ancient Greek, Greek: ...
at 2 months gestational age, mainly from the
thymus The thymus is a specialized primary Lymphatic system#Structure, lymphoid organ of the immune system. Within the thymus, T cell, thymus cell lymphocytes or ''T cells'' mature. T cells are critical to the adaptive immune system, where the body ad ...

thymus
and the
spleen The spleen is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's ...

spleen
.
Lymphocytes A lymphocyte is a type of white blood cell in the immune system of gnathostomata, jawed vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated immunity, cell-mediated, cytotoxicity, cytotoxic innate immune system, i ...

Lymphocytes
derived from the thymus are called
T lymphocyte A T cell is a type of lymphocyte A lymphocyte is a type of white blood cell in the immune system The immune system is a network of biological processes that protects an organism In biology, an organism (from Ancient Greek, Greek: ...

T lymphocyte
s (T cells), whereas those derived from
bone marrow Bone marrow is a semi-solid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphos ...
are called B lymphocytes (B cells). Both of these populations of lymphocytes have short-lived and long-lived groups. Short-lived T cells usually reside in thymus, bone marrow and spleen; whereas long-lived T cells reside in the blood stream.
Plasma cells Plasma cells, also called plasma B cells, are white blood cells White blood cells (WBCs), also called leukocytes or leucocytes, are the cells of the immune system The immune system is a network of biological processes that protects an o ...

Plasma cells
are derived from B cells and their life in fetal blood is 0.5 to 2 days.


Glands

The
thyroid The thyroid, or thyroid gland, is an endocrine gland Endocrine glands are ductless glands of the endocrine system The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organi ...

thyroid
is the first
gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormone A hormone (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλά ...

gland
to develop in the embryo at the 4th week of gestation.
Insulin Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets; it is considered to be the main Anabolism, anabolic hormone of the body. It regulates the metabolism of carbohydrates, fats and p ...

Insulin
secretion in the fetus starts around the 12th week of gestation.


Cognitive development

Initial knowledge of the effects of prenatal experience on later neuropsychological development originates from the Dutch Famine Study, which researched the cognitive development of individuals born after the
Dutch famine of 1944–45 The Dutch famine of 1944–45, known in the Netherlands as the ''Hongerwinter'' (literal translation: hunger winter), was a famine that took place in the History of the Netherlands (1939–1945), German-occupied Netherlands, especially in the den ...
. The first studies focused on the consequences of the famine to cognitive development, including the prevalence of intellectual disability.Stein, Z., Susser, M., Saenger, G., & Marolla, F. (1972). Nutrition and mental performance. Science, 178(62),708-713. Such studies predate David Barker's hypothesis about the association between the prenatal environment and the development of chronic conditions later in life. The initial studies found no association between malnourishment and cognitive development, but later studies found associations between malnourishment and increased risk for
schizophrenia Schizophrenia is a mental disorder A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such features may b ...

schizophrenia
, antisocial disorders, and affective disorders. There is evidence that the acquisition of language begins in the prenatal stage. After 26 weeks of gestation, the peripheral auditory system is already fully formed. Also, most low-frequency sounds (less than 300 Hz) can reach the fetal inner ear in the womb of mammals. Those low-frequency sounds include pitch, rhythm, and phonetic information related to language. Studies have indicated that fetuses react to and recognize differences between sounds. Such ideas are further reinforced by the fact that newborns present a preference for their mother's voice, present behavioral recognition of stories only heard during gestation, and (in monolingual mothers) present preference for their native language. A more recent study with
EEG Electroencephalography (EEG) is an electrophysiological monitoring method to record electrical activity on the scalp The scalp is the anatomical area bordered by the human face at the front, and by the neck at the sides and back. Structure ...
demonstrated different brain activation in newborns hearing their native language compared to when they were presented with a different language, further supporting the idea that language learning starts while in gestation.


Growth rate

Growth rate of fetus is linear up to 37 weeks of gestation, after which it plateaus. The growth rate of an embryo and infant can be reflected as the weight per
gestational age Gestational age is a measure of the age of a pregnancy Pregnancy, also known as gestation, is the time during which one or more offspring In biology, offspring are the young creation of living organisms, produced either by a Asexual repr ...
, and is often given as the weight put in relation to what would be expected by the gestational age. A baby born within the normal range of weight for that gestational age is known as appropriate for gestational age (AGA). An abnormally slow growth rate results in the infant being
small for gestational age Small for gestational age (SGA) newborns are those who are smaller in size than normal for the gestational age, most commonly defined as a weight below the 10th percentile for the gestational age. Causes Being small for gestational age is broadly ...
, and, on the other hand, an abnormally large growth rate results in the infant being large for gestational age. A slow growth rate and
preterm birth Preterm birth, also known as premature birth, is the Childbirth, birth of a baby at fewer than 37 weeks gestational age, as opposed to full-term delivery at approximately 40 weeks. Very early preterm birth is before 32 weeks, early preterm birth ...
are the two factors that can cause a
low birth weight Low birth weight (LBW) is defined by the World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations United Nations Specialized Agencies are autonomous organizations working with the United N ...
. Low birth weight (below 2000 grams) can slightly increase the likelihood of schizophrenia. The growth rate can be roughly correlated with the
fundal height Fundal height, or McDonald's rule, is a measure of the size of the uterus used to assess Gestational age, fetal growth and development during pregnancy. It is measured from the top of the mother's uterus to the top of the mother's pubic symphysis ...

fundal height
which can be estimated by abdominal palpation. More exact measurements can be performed with
obstetric ultrasonography Obstetric Obstetrics is the field of study concentrated on pregnancy, childbirth and the postpartum period. As a medical specialty, obstetrics is combined with gynecology under the discipline known as obstetrics and gynecology (OB/GYN), which is ...
.


Factors influencing development

Intrauterine growth restriction Intrauterine growth restriction (IUGR) refers to poor growth of a fetus while in the mother's womb during pregnancy. The causes can be many, but most often involve poor maternal nutrition or lack of adequate oxygen supply to the fetus. At least ...
is one of the causes of
low birth weight Low birth weight (LBW) is defined by the World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations United Nations Specialized Agencies are autonomous organizations working with the United N ...
associated with over half of neonatal deaths.


Poverty

Poverty has been linked to poor prenatal care and has been an influence on prenatal development. Women in poverty are more likely to have children at a younger age, which results in low birth weight. Many of these expecting mothers have little education and are therefore less aware of the risks of
smoking Smoking is a practice in which a substance is burned and the resulting smoke Smoke is a collection of airborne and es emitted when a material undergoes or , together with the quantity of air that is or otherwise mixed into the ma ...

smoking
, drinking
alcohol In chemistry, alcohol is an organic compound that carries at least one hydroxyl functional group (−OH) bound to a Saturated and unsaturated compounds, saturated carbon atom. The term alcohol originally referred to the primary alcohol ethan ...
, and drug use other factors that influence the growth rate of a fetus.


Mother's age

Women between the ages of 16 and 35 have a healthier environment for a fetus than women under 16 or over 35. Women between this age gap are more likely to have fewer complications. Women over 35 are more inclined to have a longer labor period, which could potentially result in death of the mother or fetus. Women under 16 and over 35 have a higher risk of preterm labor (premature baby), and this risk increases for women in poverty, women who take drugs, and women who smoke. Young mothers are more likely to engage in high risk behaviors, such as using alcohol, drugs, or smoking, resulting in negative consequences for the fetus. Premature babies from young mothers are more likely to have neurological defects that will influence their coping capabilities irritability, trouble sleeping, constant crying for example. There is an increased risk of
Down syndrome Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome In the fields of molecular biology and genetics Gen ...
for infants born to those aged over 40 years. Young teenaged mothers (younger than 16) and mothers over 35 are more exposed to the risks of miscarriages, premature births, and birth defects.


Drug use

An estimated 5 percent of fetuses in the United States are exposed to illicit drug use during pregnancy. Maternal drug use occurs when drugs ingested by the pregnant woman are metabolized in the placenta and then transmitted to the fetus. Resent research display that there is a correlation between fine motor skills and prenatal risk factors such as the use of psychoactive substances and signs of abortion during pregnancy. As well as perinatal risk factors such as gestation time, duration of delivery, birth weight and postnatal risk factors such as constant falls.


Cannabis

When using
cannabis ''Cannabis'' () is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including ...

cannabis
, there is a greater risk of birth defects, low birth weight, and a higher rate of death in infants or stillbirths. Drug use will influence extreme irritability, crying, and risk for SIDS once the fetus is born. Marijuana will slow the fetal growth rate and can result in premature delivery. It can also lead to low birth weight, a shortened gestational period and complications in delivery. Cannabis use during pregnancy was unrelated to risk of perinatal death or need for special care, but, the babies of women who used cannabis at least once per week before and throughout pregnancy were 216g lighter than those of non‐users, had significantly shorter birth lengths and smaller head circumferences.


Opioids

Opioid Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid use ...
s including
heroin Heroin, also known as diacetylmorphine and diamorphine among other names, is an opioid Opioids are substances that act on opioid receptor Opioid receptors are a group of inhibitory G protein-coupled receptors with opioids as ligands. T ...

heroin
will cause interrupted fetal development, stillbirths, and can lead to numerous birth defects. Heroin can also result in premature delivery, creates a higher risk of miscarriages, result in facial abnormalities and head size, and create gastrointestinal abnormalities in the fetus. There is an increased risk for SIDS, dysfunction in the central nervous system, and neurological dysfunctions including tremors, sleep problems, and seizures. The fetus is also put at a great risk for low birth weight and respiratory problems.


Cocaine

Cocaine use results in a smaller brain, which results in learning disabilities for the fetus. Cocaine puts the fetus at a higher risk of being stillborn or premature. Cocaine use also results in low birthweight, damage to the central nervous system, and motor dysfunction. The vasoconstriction of the effects of cocaine lead to a decrease in placental blood flow to the fetus that results in fetal hypoxia that is oxygen deficiency and decreased fetal nutrition these vasoconstrictive effects on the placenta have been linked to the number of complications in malformations that are evident in the newborn.


Methamphetamine

Prenatal methamphetamine exposure has shown to negatively impact brain development and behavioral functioning. A 2019 study further investigated neurocognitive and neurodevelopmental effects of prenatal methamphetamine exposure. This study had two groups, one containing children who were prenatally exposed to methamphetamine but no other illicit drugs and one containing children who met diagnosis criteria for ADHD but were not prenatally exposed to any illicit substance. Both groups of children completed intelligence measures to compute an IQ. Study results showed that the prenatally exposed children performed lower on the intelligence measures than their non-exposed peers with ADHD. The study results also suggest that prenatal exposure to methamphetamine may negatively impact processing speed as children develop.


Alcohol

Maternal alcohol use leads to disruptions of the fetus's brain development, interferes with the fetus's cell development and organization, and affects the maturation of the central nervous system. Even small amounts of alcohol use can cause lower height, weight and head size at birth and higher aggressiveness and lower intelligence during childhood.
Fetal alcohol spectrum disorder Fetal alcohol spectrum disorders (FASDs) are a group of conditions that can occur in a person whose mother drank alcohol during pregnancy. Symptoms can include an abnormal appearance, short height, low body weight, small head size, poor coordi ...
is a developmental disorder that is a consequence of heavy alcohol intake by the mother during pregnancy. Children with FASD have a variety of distinctive facial features, heart problems, and cognitive problems such as developmental disabilities, attention difficulties, and memory deficits.


Tobacco use

Tobacco smoking Tobacco smoking is the practice of burning tobacco Tobacco is the common name of several plants in the ' of the , and the general term for any product prepared from the of these plants. of tobacco are known, but the chief commerci ...

Tobacco smoking
during pregnancy exposes the fetus to nicotine, tar, and
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom. It is the simplest molecule of the oxocarbon family. In ...

carbon monoxide
. Nicotine results in less blood flow to the fetus because it constricts the blood vessels. Carbon monoxide reduces the oxygen flow to the fetus. The reduction of blood and oxygen flow may result in miscarriage, stillbirth, low birth weight, and premature births. Exposure to secondhand smoke leads to higher risks of low birth weight and childhood cancer.


Infections

If a mother is with a disease, the placenta cannot always filter out the
pathogen In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanism ...
s.
Virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...

Virus
es such as
rubella Rubella, also known as German measles or three-day measles, is an infection An infection is the invasion of an organism's body by , their multiplication, and the reaction of tissues to the infectious agents and the s they produce. An inf ...

rubella
,
chicken pox Chickenpox, also known as varicella, is a highly contagious disease caused by the initial infection An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, a ...
,
mumps Mumps is a viral disease A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infection, infectious virus particles (virions) attach to and enter susceptible cells. Structural characteris ...

mumps
,
herpes Herpes simplex is a viral infection A viral disease (or viral infection) occurs when an organism's body is invaded by pathogen In biology Biology is the natural science that studies life and living organisms, including their anatomy ...
, and
human immunodeficiency virus The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause AIDS, acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the ...
(HIV) are associated with an increased risk of
miscarriage Miscarriage, also known in medical terms as a spontaneous abortion and pregnancy loss, is the natural loss of an embryo An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism ...
,
low birth weight Low birth weight (LBW) is defined by the World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations United Nations Specialized Agencies are autonomous organizations working with the United N ...
, prematurity, physical malformations, and intellectual disabilities. HIV can lead to
acquired immune deficiency syndrome Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection An infection is the invasion of an organism's body tissues by disease-causing agents, their mult ...
(AIDS). Untreated HIV carries a risk of between 10 and 20 per cent of being passed on to the fetus. Bacterial or parasitic diseases may also be passed on to the fetus, and include
chlamydia Chlamydia, or more specifically a chlamydia infection, is a sexually transmitted infection caused by the bacterium '' Chlamydia trachomatis''. Most people who are infected have no symptoms. When symptoms do appear it can be several weeks after ...
,
syphilis Syphilis is a sexually transmitted infection Sexually transmitted infections (STIs), also referred to as sexually transmitted diseases (STDs) and the older term venereal disease, are infection An infection is the invasion of an orga ...
,
tuberculosis Tuberculosis (TB) is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to the in ...

tuberculosis
,
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign fo ...

malaria
, and commonly
toxoplasmosis Toxoplasmosis is a parasitic disease caused by ''Toxoplasma gondii'', an apicomplexan. Infections with toxoplasmosis usually cause no obvious symptoms in adults. Occasionally, people may have a few weeks or months of mild, flu-like illness such as ...
. Toxoplasmosis can be acquired through eating infected undercooked meat or contaminated food, and by drinking contaminated water. The risk of fetal infection is lowest during early pregnancy, and highest during the third trimester. However, in early pregnancy the outcome is worse, and can be fatal.


Maternal nutrition

Adequate nutrition is needed for a healthy fetus. Mothers who gain less than 20 pounds during pregnancy are at increased risk for having a preterm or low birth weight infant. Iron and iodine are especially important during prenatal development. Mothers who are deficient in iron are at risk for having a preterm or low birth weight infant. Iodine deficiencies increase the risk of miscarriage, stillbirth, and fetal brain abnormalities. Adequate
prenatal care Prenatal care, also known as antenatal care, is a type of preventive healthcare Preventive healthcare, or prophylaxis, consists of measures taken for disease prevention.Hugh R. Leavell and E. Gurney Clark as "the science and art of preventing ...
gives an improved result in the
newborn An infant (from the Latin word ''infans'', meaning 'unable to speak' or 'speechless') is the more formal or specialised synonym for the common term ''baby'', meaning the of . The term may also be used to refer to of other organisms. A n ...
.


Low birth weight

Low birth weight Low birth weight (LBW) is defined by the World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations United Nations Specialized Agencies are autonomous organizations working with the United N ...
increases an infants risk of long-term growth and cognitive and language deficits. It also results in a shortened gestational period and can lead to prenatal complications.


Stress

Stress during pregnancy can impact the development of the embryo. Reilly (2017) states that stress can come from many forms of life events such as community, family, financial issues, and natural causes. While a woman is pregnant, stress from outside sources can take a toll on the growth in the womb that may affect the child's learning and relationships when born. For instance, they may have behavioral problems and might be antisocial. The stress that the mother experiences affects the fetus and the fetus' growth which can include the fetus' nervous system (Reilly, 2017). Stress can also lead to low birth weight. Even after avoiding other factors like alcohol, drugs, and being healthy, stress can have its impacts whether families know it or not. Many women who deal with maternal stress do not seek treatment. Similar to stress, Reilly stated that in recent studies, researchers have found that pregnant women who show depressive symptoms are not as attached and bonded to their child while it is in the womb (2017).


Environmental toxins

Exposure to
environmental toxins in pregnancy A biophysical environment is a biotic and abiotic surrounding of an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, ...
lead to higher rates of miscarriage, sterility, and birth defects. Toxins include fetal exposure to lead, mercury, and ethanol or hazardous environments. Prenatal exposure to mercury may lead to physical deformation, difficulty in chewing and swallowing, and poor motoric coordination. Exposure to high levels of lead prenatally is related to prematurity, low birth weight, brain damage, and a variety of physical defects. Exposure to persistent
air pollution Air pollution is the presence of substances in the atmosphere that are harmful to the health of humans and other Outline of life forms, living beings, or cause damage to the climate or to materials. There are different types of air pollutants, ...

air pollution
from traffic and
smog Smog, or smoke fog, is a type of intense air pollution Air pollution is the presence of substances in the atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', mea ...

smog
may lead to reduced infant head size, low birth weight, increased infant death rates, impaired lung and immune system development.


See also

* Prenatal memory * Prenatal and perinatal psychology * Fetal pig * Timeline of human prenatal development * Transplacental carcinogenesis


References


Further reading

* * * * * *"Prenatal Development Prenatal Environmental Influences Mother, Birth, Fetus, and Pregnancy." Social Issues Reference. Version Child Development Vol. 6. N.p., n.d. Web. 19 Nov. 2012. . *Niedziocha, Laura. "The Effects of Drugs And Alcohol on Fetal Development , LIVESTRONG.COM." LIVESTRONG.COM Lose Weight & Get Fit with Diet, Nutrition & Fitness Tools , LIVESTRONG.COM. N.p., 4 Sept. 2011. Web. 19 Nov. 2012. . * * *Brady, Joanne P., Marc Posner, and Cynthia Lang. "Risk and Reality: The Implications of Prenatal Exposure to Alcohol and Other Drugs ." ASPE. N.p., n.d. Web. 19 Nov. 2012. .


External links


Chart of human fetal development
U.S. National Library of Medicine (NLM)
U.K. Human Fertilisation and Embryology Authority (HFEA)
regulatory agency overseeing the use of gametes and embryos in fertility treatment and research {{DEFAULTSORT:Prenatal Development Embryology Fertility Midwifery