Pulmonary hypoplasia with an unusual prenatal history.

We describe a monochorionic, diamniotic twin with renal agenesis who received amniotic fluid from his normal co-twin by spontaneous rupture of the amniotic septum between them. By 16 weeks of gestation the presence of severe oligohydramnios in one twin had resulted in renal agenesis, but not in the other twin, who did not have oligohydramnios. By 20 weeks of gestation, the two amniotic fluid volumes had become the same in both twins. At 33 weeks, the twins were delivered by cesarean section. Despite intensive respiratory care, the twin with renal agenesis died from severe pneumomediastinum on day 3. At autopsy, pulmonary hypoplasia was demonstrated in that twin. This experiment of nature demonstrates that oligohydramnios during the early canalicular stage of pulmonary development (gestational age, 16-20 weeks) may be pathogenically important in pulmonary hypoplasia.