Fetal pyelectasis in consecutive pregnancies: a possible genetic predisposition.

Mild fetal pyelectasis is a relatively common finding. The objective of this study was to assess its recurrence rate in subsequent pregnancies. The study comprised 420 women with two consecutive normal uncomplicated pregnancies screened at 15-24 weeks' gestation by ultrasound. Pyelectasis was defined as a fetal pelvis of 4 mm or more in its anterior-posterior dimensions. Of 64 fetuses with pyelectasis, 43 (67%) had a recurrence of this finding in their subsequent pregnancy. Compared with normal fetuses, those with pyelectasis had a relative risk of 6.1 to have a recurrence of this finding in their next pregnancy (95% confidence interval, 4.3-7.5, p < 0.001). These results suggest a predisposition for pyelectusis that may be influenced by genetic and/or environmental factors. More data are needed before an accurate adjustment based on previous results can be made.