Impact of screening for large-for-gestational-age fetuses on maternal and neonatal outcomes: a prospective observational study.

Objectives: Debates on the management of macrosomia are still current. We have to consider the consequences of screening to contribute to these discussions. Our aim is to study the consequences of the 3rd trimester fetal macrosomia screening protocols used in several centres in the same French region in order to determine whether this screening affects maternal and neonatal outcomes: mode of delivery, maternal complications (haemorrhage, perineal lesions), neonatal health (pH, Apgar score) and the occurrence of neonatal trauma during delivery.

Methods: Prospective observational, multicenter cohort study (Reims, Châlons en Champagne and Charleville-Mézières hospitals). All women with low-risk pregnancies who could benefit from screening for fetal macrosomia were included. Neonatal macrosomia was defined as a weight above the 90th percentile according to AUDIPOG adjusted growth curves. The principal outcome was the cesarean section rate. Secondary outcomes were instrumental deliveries and maternal and neonatal morbidity and mortality.

Results: 2,217 women were included. Rates of cesarean section and instrumental delivery were higher if macrosomia had been screened, whether rightly, in large-for-gestational-age newborns (respectively 9,802 [1.638-190.290], p=0.038 and 3,021 [1.099-8.846], p=0.036) or wrongly, in newborns who were ultimately appropriate-for-date (respectively ORa 3.562 [1.377-10.128], p=0.01 and 3.042 [1.139-8.596], p=0.36). This screening did not reduce maternal and neonatal morbidity and mortality.

Conclusions: Screening for fetal macrosomia may be associated with increased rates of cesarean section and instrumental delivery for large-for-gestational-age and appropriate-for-date newborns. These results do not show any impact of these variations on maternal or neonatal health, and do not allow us to change practices directly. They do, however, alert us to the consequences of widespread screening for LGA and its possible side effects, which could be better targeted to high-risk populations or improved according to other criteria.