ISOLATED MILD FETAL PYELECTASIS DETECTED BY TRANSVAGINAL SONOGRAPHY IN ADVANCED MATERNAL AGE

Objective: To evaluate the importance and evolution of isolated, mild fetal pyelectasis, detected in early pregnancy by high-resolution tran svaginal sonography, and to determine its association with abnormal fe tal karyotypes. Methods: Transvaginal scan at 11-16 weeks' gestation a nd transabdominal ultrasound examinations at the time of amniocentesis (16-18 weeks) were performed in 1093 pregnant women undergoing geneti c amniocentesis because of advanced maternal age. In 795 cases, transa bdominal scans were repeated at 22-24 weeks. Women were excluded if th ey had a spontaneous abortion, chose to terminate their pregnancy, or declined amniocentesis. Each patient was screened for fetal pyelectasi s, defined as an increase in anteroposterior renal pelvic diameter, us ing cutoff values related to various stages of pregnancy. Results: Iso lated fetal pyelectasis was detected at the first ultrasound examinati on in 56 women (5.1%) in early pregnancy, in 32 (2.9%) at the time of amniocentesis, and in 23 (2.9%) at 22-24 weeks' gestation. Two fetuses with diagnoses of mild pyelectasis at the first transvaginal ultrasou nd demonstrated abnormal karyotypes at amniocentesis. In one case, the pyelectasis disappeared at 22-24 weeks' gestation. Conclusion: This r etrospective study shows that pyelectasis is more frequently detectabl e by high-resolution transvaginal sonography in the first half of preg nancy than in the second half. When detected in early pregnancy, the f inding is frequently transient and not associated with an increased ri sk of abnormal fetal karyotypes. (Obstet Gynecol 1998;92: 833-6. (C) 1 998 by The American College of Obstetricians and Gynecologists.).