Unexplained second trimester oligohydramnios: a clinical-pathologic study.

The importance of oligohydramnios in the absence of fetal malformations has been recognized because of the associated high risk for adverse pregnancy outcome. Pathologic dissections were performed on four fresh fetuses whose mothers were identified by ultrasound as having oligohydramnios and had no clinical history or physical evidence of vaginal leakage of amniotic fluid. The fetuses were all normal except for hypoplasia of the lungs and varying degrees of Potter's facies. The kidneys were histologically normal but had increased weight. The more widespread use of ultrasound may have allowed us to detect an earlier stage of a previously present type of pregnancy failure.