Fetal hydrocephaly: diagnosis, prognosis and management.

Ventricle/hemisphere (V/H) ratio and head circumference (HC) measurements were obtained in 230 normal pregnancies between 16 and 28 weeks of gestation. The mean V/H ratio demonstrated a gradual decrease from 0.50 at 16 weeks to 0.26 at 26-28 weeks. HC showed a linear increase from 133 mm at 16 weeks to 268 mm at 28 weeks. In 9 other pregnancies, fetal hydrocephaly was established by routine ultrasound before 26 weeks of gestation. Whereas all V/H ratio values were situated above the upper normal limit, most of the corresponding HC values (6/9) were within the normal range. Severe hydrocephaly (V/H ratio greater than 3X upper confidence interval) was established in 7 out of 9 fetuses; associated intra or extra cranial structural anomalies were observed in 6 out of 9 fetuses. The implications of these findings for obstetric management of hydrocephaly are discussed.