Oligohydramnios Sequence Health Article

Demographics

There is no one group of individuals or one particular sex that have a higher risk to develop oligohydramnios sequence. Although, some of the inherited conditions that have been associated with oligohydramnios sequence may be more common in certain regions of the world or in certain ethnic groups.

Signs and symptoms

With severe oligohydramnios, because of the lack of amniotic fluid, the amniotic cavity remains small, thereby constricting the fetus. As the fetus grows, the amniotic cavity tightens around the fetus, inhibiting normal growth and development. This typically results in the formation of certain facial features, overall small size, wrinkled skin, and prevents the arms and legs from moving.

The facial features seen in oligohydramnios sequence include a flattened face, wide-set eyes, a flattened, beaked nose, ears set lower on the head than expected (low-set ears), and a small, receding chin (micrognathia).

Because the movement of the arms and legs are restricted, a variety of limb deformities can occur, including bilateral clubfoot (both feet turned to the side), dislocated hips, broad flat hands and joint contractures (inability for the joints to fully extend). Contractures tend to be seen more often in fetuses where the oligohydramnios occurred during the second trimester. Broad, flat hands tend to be seen more often in fetuses where the oligohydramnios began during the third trimester.

Fetuses with oligohydramnios sequence also tend to have pulmonary hypoplasia (underdevelopment of the lungs). The pulmonary hypoplasia is felt to occur as a result of the compression of the fetal chest (thorax), although it has been suggested that pulmonary hypoplasia may develop before 16 weeks of pregnancy in some cases. Therefore, regardless of the cause of the severe oligohydramnios, the physical features that develop and are seen in oligohydramnios sequence tend to be the same.

Diagnosis

An ultrasound examination during the second and/or third trimester of a pregnancy is a good tool to help detect the presence of oligohydramnios. Since oligohydramnios can occur later in a pregnancy, an ultrasound examination performed during the second trimester may not detect the presence of oligohydramnios. In pregnancies affected with oligohydramnios, an ultrasound examination can be difficult to perform because there is less amniotic fluid around the fetus. Therefore, an ultrasound examination may not be able to detect the underlying cause of the oligohydramnios.

In some situations, an amnioinfusion (injection of fluid into the amniotic cavity) is performed. This can sometimes help determine if the cause of the oligohydramnios was leakage of the amniotic fluid. Amnioinfusions may also be used to help visualize the fetus on ultrasound in attempts to detect any fetal abnormalities.

Additionally, maternal serum screening may detect the presence of oligohydramnios in a pregnancy. Maternal serum screening is a blood test offered to pregnant women to help determine the chance that their baby may have Down syndrome, Trisomy 18, and spina bifida. This test is typically performed between the fifteenth and twentieth week of a pregnancy. The test works by measuring amount of certain substances in the maternal circulation.

Alpha-fetoprotein (AFP) is a protein produced mainly by the fetal liver and is one of the substances measured in the mother's blood. The level of AFP in the mother's blood has been used to help find pregnancies at higher risk to have spina bifida. An elevated AFP in the mother's blood, which is greater than 2.5 multiples of the median (MoM), has also been associated with several conditions, including the presence of oligohydramnios in a pregnancy. Since oligohydramnios is just one of several explanations for an elevated AFP level, an ultrasound examination is recommended when there is an elevated AFP level. However, not all pregnancies affected with oligohydramnios will have an elevated AFP level, some pregnancies with oligohydramnios will have the AFP level within the normal range.

Because fetuses with oligohydramnios sequence can have other anomalies, a detailed examination of the fetus should be performed. Knowing all the abnormalities a fetus has is important in making an accurate diagnosis. Knowing the cause of the oligohydramnios and if it is related to a syndrome or genetic condition is essential in predicting the chance for the condition to occur again in a future pregnancy. Sometimes the fetal abnormalities can be detected on a prenatal ultrasound examination or on an external examination of the fetus after delivery. However, several studies have shown that an external examination of the fetus can miss some fetal abnormalities and have stressed the importance of performing an autopsy to make an accurate diagnosis.

Treatment and management

There is currently no treatment or prevention for oligohydramnios sequence. Amnioinfusions, which can assist in determining the cause of the oligohydramnios in a pregnancy, is not recommended as a treatment for oligohydramnios sequence.