Serial plotting of symphysis-fundal height and estimated fetal weight to improve the antenatal detection of infants small for gestational age: A cluster randomised trial

Objective: To assess whether standardised longitudinal reporting of growth monitoring information improves antenatal detection of infants who are small for gestational age (SGA), compared with usual care.

Design: Cluster-randomised controlled trial.

Setting: Sixteen French level-3 units in 2018-2019.

Population: Singleton pregnancies.

Methods: The intervention consisted of the serial plotting of symphysis-fundal height (SFH) and estimated fetal weight (EFW) measurements on customised growth charts using a software program, compared with standard antenatal care. We estimated relative risks (RR) adjusted for known risk factors for fetal growth restriction (FGR).

Main outcome measures: The primary outcome was antenatal detection of FGR among SGA births (with birthweights below the tenth centile of French customised curves), defined as the mention of suspected FGR in medical records and either referral ultrasounds for growth monitoring or indicated delivery for FGR. Secondary outcomes were false-positive rates, mode of delivery, perinatal morbidity and mortality, and number of antenatal visits and ultrasounds.

Results: In total, seven intervention clusters (n = 4349) and eight control clusters (n = 4943) were analysed, after the exclusion of one intervention centre for a major deviation in protocol. SGA births represented 613 (14.1%) and 626 (12.7%) of all births, respectively. The rates of antenatal detection of FGR among SGA births were 40.0% in the intervention arm versus 37.1% in the control arm (crude RR 1.08, 95% CI 0.87-1.34; adj RR 1.09, 95% CI 0.88-1.35). No benefits of the intervention were detected in the analyses of secondary outcomes.

Conclusions: Serial plotting of SFH and EFW measurements on customised growth charts did not improve the antenatal detection of FGR among SGA births.