Polyhydramnios is a medical condition describing an excess of

amniotic fluid The amniotic fluid is the protective liquid contained by the amniotic sac of a gravid amniote. This fluid serves as a cushion for the growing fetus, but also serves to facilitate the exchange of nutrients, water, and biochemical products between ...

in the

amniotic sac The amniotic sac, also called the bag of waters or the membranes, is the sac in which the embryo and later fetus develops in amniotes. It is a thin but tough transparent pair of membranes that hold a developing embryo (and later fetus) until sh ...

. It is seen in about 1% of pregnancies. It is typically diagnosed when the

amniotic fluid index Amniotic fluid index (AFI) is a quantitative estimate of amniotic fluid and an indicator of fetal well-being. It is a separate measurement from the biophysical profile. AFI is the score (expressed in cm) given to the amount of amniotic fluid see ...

(AFI) is greater than 24 cm. There are two clinical varieties of polyhydramnios: chronic polyhydramnios where excess amniotic fluid accumulates gradually, and acute polyhydramnios where excess amniotic fluid collects rapidly. The opposite to polyhydramnios is

oligohydramnios Oligohydramnios is a medical condition in pregnancy characterized by a deficiency of amniotic fluid, the fluid that surrounds the fetus in the abdomen, in the amniotic sac. It is typically diagnosed by ultrasound when the amniotic fluid index ( ...

, not enough amniotic fluid.

Presentation

Associated conditions

Fetuses with polyhydramnios are at risk for a number of other problems including

cord prolapse Umbilical cord prolapse is when the umbilical cord comes out of the uterus with or before the presenting part of the baby. The concern with cord prolapse is that pressure on the cord from the baby will compromise blood flow to the baby. It usua ...

placental abruption Placental abruption is when the placenta separates early from the uterus, in other words separates before childbirth. It occurs most commonly around 25 weeks of pregnancy. Symptoms may include vaginal bleeding, lower abdominal pain, and dang ...

premature birth Preterm birth, also known as premature birth, is the birth of a baby at fewer than 37 weeks gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 weeks, very early preterm birth is between ...

and perinatal death. At delivery the baby should be checked for congenital abnormalities.

Causes

In most cases, the exact cause cannot be identified. A single case may have one or more causes, including intrauterine infection (

TORCH A torch is a stick with combustible material at one end, which is ignited and used as a light source. Torches have been used throughout history, and are still used in processions, symbolic and religious events, and in juggling entertainment. I ...

), rh-isoimmunisation, or chorioangioma of the placenta. In a multiple gestation pregnancy, the cause of polyhydramnios usually is

twin-to-twin transfusion syndrome Twin-to-twin transfusion syndrome (TTTS), also known as feto-fetal transfusion syndrome (FFTS), twin oligohydramnios-polyhydramnios sequence (TOPS) and stuck twin syndrome, is a complication of monochorionic multiple pregnancies (the most comm ...

. Maternal causes include

cardiac The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to t ...

problems,

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blo ...

problems, and maternal

diabetes mellitus Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...

, which causes fetal

hyperglycemia Hyperglycemia is a condition in which an excessive amount of glucose circulates in the blood plasma. This is generally a blood sugar level higher than 11.1 mmol/L (200 mg/dL), but symptoms may not start to become noticeable until even ...

and resulting

polyuria Polyuria () is excessive or an abnormally large production or passage of urine (greater than 2.5 L or 3 L over 24 hours in adults). Increased production and passage of urine may also be termed diuresis. Polyuria often appears in conjunction wi ...

(fetal urine is a major source of amniotic fluid). A recent study distinguishes between mild and severe polyhydramnios and showed that

Apgar score The Apgar score is a quick way for doctors to evaluate the health of all newborns at 1 and 5 minutes after birth and in response to resuscitation. It was originally developed in 1952 by an anesthesiologist at Columbia University, Virginia Apgar ...

of less than 7, perinatal death and structural malformations only occurred in women with severe polyhydramnios. In another study, all patients with polyhydramnios, that had a sonographically normal fetus, showed no chromosomal anomalies. (M/C for polyhydramnio is fetal anomalies 'Williams Obstetrics, 24th Edition – Cunningham, Leveno, Bloom et al. Table 11–2) but these anomalies include: *

gastrointestinal The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...

abnormalities such as

esophageal atresia Esophageal can refer to: * The esophagus * Esophageal arteries * Esophageal glands * Esophageal cancer Esophageal cancer is cancer arising from the esophagus—the food pipe that runs between the throat and the stomach. Symptoms often include ...

and duodenal atresia (causing inability to swallow amniotic fluid), anencephaly, facial cleft, neck masses, tracheoesophageal fistula, and diaphragmatic hernias. An annular pancreas causing obstruction may also be the cause. *Bochdalek's hernia, in which the pleuro-peritoneal membranes (especially the left) will fail to develop and seal the pericardio-peritoneal canals. This results in the stomach protrusion up into the thoracic cavity, and the fetus is unable to swallow sufficient amounts of amniotic fluid. * fetal

renal The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; bloo ...

disorders that result in increased urine production during pregnancy, such as in antenatal

Bartter syndrome Bartter syndrome (BS) is a rare inherited disease characterised by a defect in the thick ascending limb of the loop of Henle, which results in low potassium levels (hypokalemia), increased blood pH (alkalosis), and normal to low blood pressure. T ...

. Molecular diagnosis is available for these conditions. *neurological abnormalities such as

anencephaly Anencephaly is the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development. It is a cephalic disorder that results from a neural tube defect that occurs when the rostral (head) end of the neural tube ...

, which impair the swallowing reflex. Anencephaly is failure of closure of the rostral neuropore (rostral neural tube defect). If the rostral neuropore fails to close there will be no neural mechanism for swallowing. *chromosomal abnormalities such as

Down syndrome Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual d ...

and

Edwards syndrome Edwards syndrome, also known as trisomy 18, is a genetic disorder caused by the presence of a third copy of all or part of chromosome 18. Many parts of the body are affected. Babies are often born small and have heart defects. Other features inc ...

, which is itself often associated with gastrointestinal abnormalities. *Skeletal dysplasia, or dwarfism. There is a possibility of the chest cavity not being large enough to house all of the baby's organs causing the trachea and esophagus to be restricted, not allowing the baby to swallow the appropriate amount of amniotic fluid. *sacrococcygeal

teratoma A teratoma is a tumor made up of several different types of tissue, such as hair, muscle, teeth, or bone. Teratomata typically form in the ovary, testicle, or coccyx. Symptoms Symptoms may be minimal if the tumor is small. A testicular ter ...

Diagnosis

There are several pathologic conditions that can predispose a pregnancy to polyhydramnios. These include a maternal history of

Rh incompatibility Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis foetalis, is an alloimmune condition that develops in a fetus at or around birth, when the IgG molecules (one of the five ...

between the fetus and mother, intrauterine infection, and

multiple pregnancies A multiple birth is the culmination of one multiple pregnancy, wherein the mother gives birth to two or more babies. A term most applicable to vertebrate species, multiple births occur in most kinds of mammals, with varying frequencies. Such bir ...

. During the pregnancy, certain clinical signs may suggest polyhydramnios. In the mother, the physician may observe increased abdominal size out of proportion for her weight gain and gestation age, uterine size that outpaces gestational age, shiny skin with stria (seen mostly in severe polyhydramnios), dyspnea, and chest heaviness. When examining the fetus, faint fetal heart sounds are also an important clinical sign of this condition.

Treatment

Mild asymptomatic polyhydramnios is managed expectantly. A woman with symptomatic polyhydramnios may need hospital admission.

Antacids An antacid is a substance which neutralizes stomach acidity and is used to relieve heartburn, indigestion or an upset stomach. Some antacids have been used in the treatment of constipation and diarrhea. Marketed antacids contain salts of alu ...

may be prescribed to relieve heartburn and

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of th ...

. No data support dietary restriction of salt and fluid. In some cases, amnioreduction, also known as therapeutic

amniocentesis Amniocentesis is a medical procedure used primarily in the prenatal diagnosis of genetic conditions. It has other uses such as in the assessment of infection and fetal lung maturity. Prenatal diagnostic testing, which includes amniocentesis, is n ...

, has been used in response to polyhydramnios.

References

External links

* {{Pathology of pregnancy, childbirth and the puerperium Pathology of pregnancy, childbirth and the puerperium