Abstract
To determine whether bladder size is associated with an unfavorable neonatal outcome, in the case of first-trimester megacystis. This was a retrospective observational study between 2009 and 2019 in two prenatal diagnosis centers. The inclusion criterion was an enlarged bladder (> 7 mm) diagnosed at the first ultrasound exam between 11 and 13+6 weeks of gestation. The main study endpoint was neonatal outcome based on bladder size. An adverse outcome was defined by the completion of a medical termination of pregnancy, the occurrence of in utero fetal death, or a neonatal death. Neonatal survival was considered as a favorable outcome and was defined by a live birth, with or without normal renal function, and with a normal karyotype. Among 75 cases of first-trimester megacystis referred to prenatal diagnosis centers and included, there were 63 (84%) adverse outcomes and 12 (16%) live births. Fetuses with a bladder diameter of less than 12.5 mm may have a favorable outcome, with or without urological problems, with a high sensitivity (83.3%) and specificity (87.3%), area under the ROC curve = 0.93, 95% CI (0.86-0.99), p< 0.001. Fetal autopsy was performed in 52 (82.5%) cases of adverse outcome. In the 12 cases of favorable outcome, pediatric follow-up was normal and non-pathological in 8 (66.7%). Bladder diameter appears to be a predictive marker for neonatal outcome. Fetuses with smaller megacystis (7-10 mm) have a significantly higher chance of progressing to a favorable outcome. Urethral stenosis and atresia are the main diagnoses made when first-trimester megacystis is observed. Karyotyping is important regardless of bladder diameter.
Highlights
First-trimester ultrasound is a fundamental element of screening policy
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Fetuses with a bladder diameter of less than 12.5 mm may have a favorable outcome, with or without urological problems, with a high sensitivity (83.3%) and specificity (87.3%), area under the receiver operating characteristic (ROC) curve = 0.93, 95% CI (0.86–0.99), p< 0.001
Summary
First-trimester ultrasound is a fundamental element of screening policy. First-trimester ultrasound seems ready to evolve from a simple screening examination to a detailed anatomical examination traditionally performed in the second trimester of pregnancy [1,2,3,4,5]. Megacystis in the first trimester of pregnancy is usually defined by a bladder size > 7 mm between 11 and 13+6 weeks of gestation [10,11,12], after checking for bladder emptying during the exam [13]. It occurs in 1/1600 to 1/3000 pregnancies. The cause may be obstructive in 60% of cases (posterior urethral valves, urethral atresia or urethral stenosis, cloacal anomalies), non-obstructive in 30% of cases, mainly syndromic disease (megacystis-microcolon-intestinal hypoperistalsis syndrome, prune belly syndrome), and idiopathic or transient (10% of cases) [14]
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