Evaluation of an optimal gestational age cut-off for the definition of early- and late-onset fetal growth restriction.

OBJECTIVE: The terms early- and late-onset fetal growth restriction (FGR) are commonly used to distinguish two phenotypes characterized by differences in onset, fetoplacental Doppler, association with preeclampsia (PE) and severity. We evaluated the optimal gestational age (GA) cut-off maximizing differences among these two forms. PATIENTS AND METHODS: A cohort of 656 consecutive singleton pregnancies with FGR was created. We used the decision tree analysis to evaluate the GA cut-off that best discriminated perinatal mortality, association with PE and adverse perinatal outcome (fetal demise, early neonatal death, neonatal acidosis at birth, and 5-min Apgar score <7).
RESULTS: We identified 32 weeks at diagnosis as the optimal cut-off, resulting in two groups with 7.1 and 0%, p < 0.001 perinatal mortality, 35.1 and 12.1%, p < 0.001 association with PE, and 13.4 and 4.6%, p < 0.001 composite adverse perinatal outcome. Abnormal versus normal umbilical artery (UA) Doppler classified two groups with 10.6 and 0.2%, p < 0.001 perinatal mortality, 50.0 and 11.8%, p < 0.001 association with PE, and 18.2 and 4.2%, p < 0.001 composite adverse perinatal outcome.
CONCLUSIONS: UA Doppler discriminated better the two forms of FGR with average early- and late-onset presentation, higher association with PE and poorer outcome. In the absence of UA information, a GA cut-off of 32 weeks at diagnosis maximizes differences between early- and late-onset FGR.