OC02.01: Term planned delivery based on fetal growth assessment with or without the cerebroplacental ratio in low‐risk pregnancies (RATIO37)

We aimed to evaluate whether the addition of cerebroplacental ratio measurement to the standard ultrasound growth assessment near term reduces perinatal mortality and severe neonatal morbidity, compared with growth assessment alone. RATIO37 was a randomised, open-label, multicentre, pragmatic trial, conducted in low-risk pregnant women, recruited from nine hospitals over six countries. In the revealed group, the CPR value was known by clinicians, and if below the 5th centile, a planned delivery after 37 weeks was recommended. In the concealed group, women and clinicians were blinded to the CPR value. All participants underwent ultrasound at 36 + 0 to 37 + 6 weeks of gestation with growth assessment and Doppler evaluation. In both groups, planned delivery was recommended when the EFW was below the10th centile. The primary outcome was perinatal mortality from 24 weeks' gestation to infant discharge. We enrolled 11214 women, of whom 9492 (84,6%) completed the trial and were eligible for analysis (4774 in the concealed group and 4718 in the revealed group). Perinatal mortality occurred in 13 (0,3%) of 4774 pregnancies in the concealed group and 13 (0,3%) of 4718 in the revealed group (OR 1,45 [95% CI 0,76–2,76]; p = 0,262). Overall, severe neonatal morbidity occurred in 35 (0,73%) newborns in the concealed group and 18 (0,38%) in the revealed group (OR 0,58 [95% CI 0,40–0,83]; p = 0,003). Severe neurological morbidity occurred in 13 (0,27%) newborns in the concealed group and nine (0,19%) in the revealed group (OR 0,56 [95% CI 0,25–1,24]; p = 0,153). Severe non-neurological morbidity occurred in 23 (0,48%) newborns in the concealed group and nine (0,19%) in the revealed group (0,58 [95% CI 0,39–0,87]; p = 0,009). Planned delivery at term based on ultrasound fetal growth assessment and CPR at term was not followed by a reduction of perinatal mortality although significantly reduced severe neonatal morbidity compared with fetal growth assessment alone.