Objective RCT and registry to determine effectiveness of VAS in LUTO for survival and renal function.

Setting Fetal Medicine departments (England, Scotland, Ireland, Netherlands).

Participants Pregnant women with singleton, male fetus with isolated LUTO.

Design RCT with registry. Intervention - VAS compared to conservative care.

Main Outcome Measures Perinatal mortality and serum creatinine at 6 weeks of age and 1 year. Prognostic value of gestational age and liquor volume at diagnosis were assessed in a logistic regression analysis using data from registry and RCT.

Results RCT survival to 28 days favoured VAS: intention-to-treat relative risk 1.88, 95%CI: 0.71 to 4.96 (50% v 27%, p = 0.27); registry favoured conservative management: relative risk 0.58, 95%CI: 0.26, 1.29 (40% v 69%, p = 0.14). Those women who entered the registry and had conservative management were more likely to have a normal liquor volume at diagnosis (>5th centile) than those receiving VAS (p = 0.04) or those randomised (p = 0.03). They also had a higher proportion with gestational age at diagnosis >24 weeks compared with those randomised (p = 0.002). These variables were strongly associated with improved survival to 28 days in a multivariate logistic regression analysis. There was also a difference in the pathological diagnoses made postnatally in the conservative group in the registry with a 5/21 (24%) of babies with a false positive antenatal diagnosis of LUTO.

Conclusion Normal liquor volume (>5th centile) and age at diagnosis > 24 weeks seem to be associated with increased probability of survival at 28 days in fetuses with confirmed LUTO.