A risk-based classification of late-onset fetal growth disorders according to intrapartum fetal compromise

Fetal growth restriction is associated with increased perinatal mortality and morbidity. We aimed to evaluate whether the combined assessment of birthweight centile (BWc) and cerebroplacental ratio expressed as multiples of the median (CPR MoM) during the late third trimester can identify distinct risk profiles for intrapartum fetal compromise (IFC) in late-onset fetal growth disorders and to propose a risk-based classification to guide birth management.

This retrospective observational study included 1530 singleton pregnancies with births between 34 and 41 weeks' gestation. All fetuses underwent antenatal ultrasound with fetal biometry and Doppler assessment of the umbilical artery pulsatility index (PI), middle cerebral artery PI, and the CPR was calculated. IFC was defined as either abnormal intrapartum cardiotocography requiring cesarean section, a fetal scalp pH < 7.20, or a neonatal pH < 7.10. Fetuses were classified into six groups according to the combination of BWc and CPR MoM.

IFC occurred in 7.25% of pregnancies. Lower BWc and abnormal CPR MoM were associated with increased IFC risk, including fetuses with BWc ≥10th centile. Fetuses with BWc <3rd centile and abnormal CPR MoM had the highest IFC risk (24.44%), while those with BWc ≥10th centile and abnormal CPR MoM also showed substantial risk (15.96%). Two groups, BWc <3rd centile with normal CPR MoM and BWc 3rd-9th centile with abnormal CPR MoM, had intermediate IFC risks, while those fetuses with BWc 3rd-9th centile and normal CPR MoM (small-for-gestational-age) presented risks comparable to fetuses with normal BWc and CPR MoM.

Late-onset fetal growth disorders represent a spectrum of placental dysfunction rather than a homogeneous pathology. Integration of BWc and CPR MoM identifies distinct risk phenotypes with different probabilities of IFC, supporting a risk-based approach to surveillance and birth management near term.