Obstetric challenges in suspected fetal macrosomia: Risk factors and assessment

Suspected fetal macrosomia is associated with increased rates of cesarean deliveries, assisted vaginal deliveries, and shoulder dystocia. Obstetric management strategies are limited by the lack of accuracy in estimating fetal weight. In this context, the associated factors for difficult delivery remain poorly defined.

To assess antenatally identified maternal and fetal factors associated with adverse obstetric outcomes in pregnancies with suspected fetal macrosomia.

Secondary analysis of a randomized controlled trial including women with suspected fetal macrosomia. The primary outcome was difficult delivery, defined as cesarean delivery, assisted vaginal delivery, and/or shoulder dystocia. Multivariable logistic regression was performed to identify maternal and fetal risk factors. Management strategy (induction of labor versus expectant management) was included according to the intention-to-treat principle.

Difficult delivery occurred in 48% of cases. Cesarean delivery was significantly associated with nulliparity (OR 4.64; 95% CI 3.23-6.47), short maternal stature (OR 1.83; 95% CI 0.96-3.48), and estimated fetal weight > 4,000 g (OR 1.59; 95% CI 1.18-2.16). Assisted vaginal delivery (15%) was associated with younger maternal age (OR 1.65; 95% CI 1.01-2.71), nulliparity (OR 7.42; 95% CI 4.70-11.70), and fetal head circumference > 340 mm (OR 1.53; 95% CI 1.02-2.29). Shoulder dystocia was associated with a head-to-abdominal circumference difference ≥ 50 mm (OR 3.68; 95% CI 1.64-8.22). Induction of labor was protective against shoulder dystocia (OR 0.29; 95% CI 0.13-0.65).

In suspected fetal macrosomia, antenatal maternal and fetal characteristics, particularly parity and fetal biometric measurements, help anticipate adverse delivery outcomes and may guide individualized management strategies.