Limb deformations in oligohydramnios sequence: effects of gestational age and duration of oligohydramnios

Oligohydramnios, regardless of cause, results in a sequence of anomalies including characteristic facies, contractures and lung hypoplasia, but the timing and duration of of oligohydramnios required to produce different features of the sequence, especially limb defects, are not well defined. Other causes of restricted fetal movement such as fetal neuromuscular disorders also result in limb contractures and lung hypoplasia. Because such neuromuscular disorders often cause polyhydramnios which in turn predisposes to premature rupture of membranes, such fetuses may present with ruptured membranes and oligohydramnios. Additional data regarding the type and incidence of limb contractures in fetuses with differing onset and duration of oligohydramnios is needed to provide accurate counseling regarding the underlying cause and recurrence risks. We have reviewed maternal histories, delivery records, pathology reports, radiographs and photographs of 90 fetuses with gestational ages from 14 weeks to term with >24 hrs documented oligohydramnios. The causes of oligohydramnios included premature rupture of membranes (44 cases), fetal renal insufficiency (25 cases), idiopathic (15 cases) and twin-twin transfusion (6 cases). The fetuses were grouped according to gestational age at delivery and duration of oligohydramnios. As expected, contractures were more frequent with earlier onset and longer duration of oligohydramnios. During the second trimester, the frequency of contractures in fetuses with oligohydramnios was 77% compared to 52% in the third trimester(p=.02). Considering all gestational ages together, 57% of fetuses had contractures after less than 2 weeks of oligohydramnios compared to 81% of fetuses with a longer duration of oligohydramnios (p<.02). The type of contracture varied with gestational age. Club foot was the most frequent at all ages, but hand contractures such as camptodactyly were common only in the second trimester while the broad flat hand originally described in Potter sequence was found almost exclusively in the third trimester. Of the 59 fetuses with oligohydramnios and contractures, 25 (42%) had either additional malformations or family history that could explain contractures independent of oligohydramnios. Oligohydramnios sequence is common in the second trimester, but presents differently compared to the third trimester and is more easily confused with other birth defects. Fetuses with oligohydramnios and contractures require a detailed examination and review of history before the contractures can be attributed to oligohydramnios sequence.