obstetrics 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 a su ...

, asynclitic birth, or asynclitism, refers to the malposition of the

fetal A fetus or foetus (; : fetuses, foetuses, rarely feti or foeti) is the unborn offspring of a viviparous animal that develops from an embryo. Following the embryonic stage, the fetal stage of development takes place. Prenatal development is a ...

head in the

uterus The uterus (from Latin ''uterus'', : uteri or uteruses) or womb () is the hollow organ, organ in the reproductive system of most female mammals, including humans, that accommodates the embryonic development, embryonic and prenatal development, f ...

relative to the

birth canal In mammals and other animals, the vagina (: vaginas or vaginae) is the elastic, muscular reproductive organ of the female genital tract. In humans, it extends from the vulval vestibule to the cervix (neck of the uterus). The vaginal int ...

. Many babies enter the

pelvis The pelvis (: pelves or pelvises) is the lower part of an Anatomy, anatomical Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also c ...

in an asynclitic

presentation A presentation conveys information from a speaker to an audience. Presentations are typically demonstrations, introduction, lecture, or speech meant to inform, persuade, inspire, motivate, build goodwill, or present a new idea/product. Presenta ...

, but in most cases, the issue is corrected during

labor Labour or labor may refer to: * Childbirth, the delivery of a baby * Labour (human activity), or work ** Manual labour, physical work ** Wage labour, a socioeconomic relationship between a worker and an employer ** Organized labour and the labour ...

. Asynclitic presentation is not the same as shoulder presentation, where the shoulder enters first. Fetal head asynclitism may affect the progression of labor, increase the need for obstetrical intervention, and be associated with difficult instrumental delivery. The prevalence of asynclitism at transperineal

ultrasound Ultrasound is sound with frequency, frequencies greater than 20 Hertz, kilohertz. This frequency is the approximate upper audible hearing range, limit of human hearing in healthy young adults. The physical principles of acoustic waves apply ...

was common in nulliparous women (those who have never given birth) at labor stage two and seemed more commonly associated with non occiput anterior position, suggesting an autocorrection typically occurs. When self-correction does not occur, obstetrical intervention is necessary. Persistent asynclitism can cause problems with

dystocia Obstructed labour, also known as labour dystocia, is the baby not exiting the pelvis because it is physically blocked during childbirth although the uterus contracts normally. Complications for the baby include not getting enough oxygen which ...

, and has often been associated with cesarean births. However, a skilled

midwife A midwife (: midwives) is a health professional who cares for mothers and Infant, newborns around childbirth, a specialisation known as midwifery. The education and training for a midwife concentrates extensively on the care of women throughou ...

obstetrician 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 a surgi ...

a complication-free vaginal birth may be achievable through movement and positioning of the mother, and patience and allowing the baby to move through the pelvis and moulding of the skull during the birthing process. Other options include the use of vacuum-assisted delivery and forceps. No evidence suggests that one asynclitic presentation predicts another in subsequent childbirth.

Diagnosis

Asynclitism can be digitally diagnosed using intrapartum

through the transabdominal cavity and the transperitoneal cavity. Intrapartum ultrasonography is regularly used during

pregnancy Pregnancy is the time during which one or more offspring gestation, gestates inside a woman's uterus. A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Conception (biology), Conception usually occurs ...

to constantly monitor the fetal position within the mother's belly. The International Society of Ultrasound in Obstetrics and Gynecology Practice Guidelines recommend the use of intrapartum ultrasound to diagnose asynclitic births during prolonged and obstructed labors. Asynclitism is most easily diagnosed during labor when the

cervix The cervix (: cervices) or cervix uteri is a dynamic fibromuscular sexual organ of the female reproductive system that connects the vagina with the uterine cavity. The human female cervix has been documented anatomically since at least the time ...

is opened allowing the orientation of the

occiput The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone lies over the occipital lobes of the ...

, the back of the fetal head, to be visually assessed in relation to the mother's pelvis. Posterior asynclitism is when the fetal occiput is facing the mother's spine, and anterior asynclitism is when the fetal occiput is facing the mother's belly. The most common and preferred type of asynclitism is the left occiput anterior asynclitism because the baby's head enters the pelvis in such a way that it minimizes the circumference of how the baby exits the body as much as possible. In this type of asynclitism, it allows the fetus to be in the most efficient position. The back of the fetus's head is towards the carrier's left side. Meanwhile, their face is towards the mother's right side at an angle between the hip and the spine of the mother. Posterior asynclitism can lengthen the duration of labor and cause complications. Asynclitism is most commonly discovered during vaginal exams conducted in labor. During the exam, the healthcare professional may feel the

parietal bone The parietal bones ( ) are two bones in the skull which, when joined at a fibrous joint known as a cranial suture, form the sides and roof of the neurocranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four bord ...

more distinctly than others. Professionals can also use ultrasound to help identify potential asynclitism.

Occurrence

Asynclitism can occur at any time during pregnancy. It most commonly occurs near the end of the third trimester or during labor, when the fetus becomes more developed and begins moving down the birth canal.

Causes

The exact cause of asynclitism is unknown. The shape and size of the uterus, the weight of the fetus, pelvic anatomy, and multiparity can contribute to it, and the likelihood of asynclitism increases if the mother has rotated hips. Situational factors include a short umbilical cord and unevenness of the pregnant person's pelvic floor during contractions, leading to the baby's head tipping to one side. Asynclitism can also begin at the time of birth. This happens when the fetus quickly comes down on the pelvic floor before straightening its head when the water breaks. This can be due to the water rushing through the pelvis too quickly and once it occurs, it is difficult to correct.

Signs and symptoms

Signs of asynclitism that may be observed without medical diagnostic equipment include visually asymmetric baby bumps, caused by the baby's head being tilted asymmetrically in relation to the mother's pelvis, or by an abnormal buildup of amniotic fluid. The mother may report symptoms of abdominal discomfort, particularly on one side, or pain on one side of the hips.

Complications

Asynclitism is common as the fetus enters through and tilts the maternal pelvis. There are three types: anterior, posterior, and lateral asynclitism. Minor asynclitism generally resolves itself and results in uncomplicated births. Minor cases present mild molding and the slight deviation of the head from the midline, but are otherwise absent of major fetal head malpositioning. In cases that present with persistent occiput posterior -- in which the head is in a downward position, but facing towards the front of the abdomen -- or shoulder positions, this can result in prolonged and difficult delivery and may warrant surgical intervention. Complications can occur before, during, and after birth that affect both parent and baby. Asynclitism can lead to slower and more difficult labor, increasing stress and fatigue. If the fetus's head is not optimally positioned, this can result in dystocia, necessitating an operative delivery. Complications are associated with procedures such as operational vaginal deliveries (OVD), particularly with the use of vacuum extraction, and

caesarean section Caesarean section, also known as C-section, cesarean, or caesarean delivery, is the Surgery, surgical procedure by which one or more babies are Childbirth, delivered through an incision in the mother's abdomen. It is often performed because va ...

s (CS). Caesarean sections can increase the risk of maternal complications, which can affect future pregnancies. These include uterine ruptures, chronic pain, hemorrhages, and bladder injury. One of the more severe complications is

placenta accreta Placenta accreta spectrum (PAS) is a medical condition that occurs when all or part of the placenta attaches abnormally to the ''myometrium'' (the muscular layer of the uterine wall) during pregnancy. This condition was first documented in medica ...

, which can lead to a life-threatening hemorrhage and peripartum hysterectomy. Complications the baby may face include

cephalohematoma A cephalohematoma (American English), also spelled cephalohaematoma (British English), is a hemorrhage of blood between the skull and the periosteum at any age, including a newborn baby secondary to rupture of blood vessels crossing the periosteu ...

hyperbilirubinemia Bilirubin (BR) (adopted from German, originally bili—bile—plus ruber—red—from Latin) is a red-orange compound that occurs in the normcomponent of the straw-yellow color in urine. Another breakdown product, stercobilin, causes the brown ...

, and

intracranial hemorrhage Intracranial hemorrhage (ICH) refers to any form of Hemorrhage, bleeding Internal bleeding, within the Human skull, skull. It can result from trauma, vascular abnormalities, hypertension, or other medical conditions. ICH is broadly categorized ...

s. Asynclitic birth can also increase the risk of birth injuries such as

brachial plexus injury A brachial plexus injury (BPI), also known as brachial plexus lesion, is an injury to the brachial plexus, the network of nerves that conducts signals from the spinal cord to the shoulder, arm and hand. These nerves originate in the fifth, sixth, s ...

, in which the nerves responsible for sending signals to the baby's arm are damaged, resulting in temporary or permanent numbness, weakness, or even paralysis in the affected arm. In rare cases, uncorrected asynclitism can lead to neonatal asphyxia, in which the child does not receive enough oxygen before, during, or just after birth, which can result in temporary or permanent organ damage. The mother may experience complications such as vaginal or cervical tears, excessive blood loss, infection of the placental membrane, and

postpartum infections Postpartum infections, also known as childbed fever and puerperal fever, are any bacterial infections of the female reproductive tract following childbirth or miscarriage. Signs and symptoms usually include a fever greater than , chills, lower ...

. Asynclitism can also affect the development of facial structures and nerves during pregnancy, with lifelong consequences for the child. These complications can include facial malformation,

Bell's palsy Bell's palsy is a type of facial paralysis that results in a temporary inability to control the facial muscles on the affected side of the face. In most cases, the weakness is temporary and significantly improves over weeks. Symptoms can vary f ...

deviated septum Nasal septum deviation is a physical disorder of the nose, involving a displacement of the nasal septum. Some displacement is common, affecting 80% of people, mostly without their knowledge. Signs and symptoms The nasal septum is the bone and ...

, and facial asymmetry.

Management

Various techniques have been tried to resolve an asynclitic position of the fetus.

Vacuum extraction Vacuum extraction (VE), also known as ventouse, is a method to assist delivery of a baby using a vacuum device. It is used in the second stage of labor if it has not progressed adequately. It may be an alternative to a forceps delivery and ca ...

, a delivery assistance method used for prolonged or obstructed labor, has been shown to reverse the position from the less optimal one, known as occiput posterior or occiput transverse, to the more favorable position known as occiput anterior. However, it is not the primary treatment for asynclitic births, as the effectiveness rate is not very high and vacuum extraction can lead to additional complications. Possible complications include fetal morbidity and fatality, and damage to the derma layer leading to bleeding within the brain and the layer of skin on the skull, known as cephalohematomas. Facial nerve damage and immobility are permanent consequences from intracranial hemorrhage, leading to a diminished quality of life. However, when it is successful, vacuum extraction can change the position from a non-occital anterior position to an occital anterior position, which is more favorable in terms of asynclitic births. Following any medical procedure to alter the occiput position or any assisted vaginal delivery, monitoring of the neonate is extremely important as intracranial hemorrhages may be imperceptible. Non-invasive techniques are typically the first steps when dealing with asynclitic birth. Short and quick breaths synchronized with contractions are commonly suggested by the obstetrician to help with prolonged labor with asynclitism. Positioning techniques can also employed to help the baby to rotate or descend. Examples of these techniques include the hands-on-knees position, lunging, kneeling lunge, side-lying release, and use of a birth ball. If positioning techniques do not work, healthcare professionals may attempt manual rotation, attempting to adjust the baby's position manually via the vagina. If none of these methods are successful, the physician may consider a caesarean section to deliver the baby safely. Along with procedural interventions, there are supportive measures that are taken to alleviate the physical and psychological trauma associated with childbirth. Supportive measures come in both non-pharmacological and pharmacological forms. For pain management, labor analgesia has been shown to be effective. Depending on the procedure, different types of anesthesia, such as pudendal block anesthesia, may be used.

Diagnosis

Occurrence

Causes

Signs and symptoms

Complications

Management

See also

References

Further reading