Early fetal megacystis: Is it possible to predict the prognosis in the first trimester?

To evaluate the best management of fetal megacystis diagnosed in the first trimester and define the prognosis and the most appropriate follow-up as early as possible.

This is a retrospective study of first-trimester fetal megacystis diagnosed in pregnant women who performed a combined screening for fetal aneuploidy. Megacystis was defined as a longitudinal bladder diameter (LBD) greater than 7 mm. All fetuses were divided into two groups according to the LBD: Group A with LBD > 15 mm and Group B with LBD < 15 mm. The fetal karyotype and associated anomalies were evaluated. Ultrasound monitoring was performed every 2 weeks (a second ultrasound scan after 2 weeks from diagnosis and a third ultrasound scan 2 weeks after the second one).

Twenty-six cases were identified between 2011 and 2016; three cases of aneuploidy were excluded from the study. Of the remaining 23 cases, 11 were included in Group A and 12 in Group B. All Group A fetuses had an adverse outcome. In Group B: five (41.7%) cases had an adverse outcome and seven (58.3%) had a spontaneous resolution of megacystis. The ultrasound findings of both the ultrasound scans, the second and the third, were 100% concordant.

An ultrasound scan performed 2 weeks after the megacystis diagnosis can predict the outcome in fetuses with an LBD < 15 mm as early as the end of the first trimester. The outcome of euploid fetuses with an LBD < 15 mm was favorable in 58.3% of the cases.