Risk of cerebral palsy by gestational age among pregnancies at-risk for preterm birth.

Objective: Our objective was to describe cerebral palsy (CP) incidence stratified by gestational age (GA) groups within a group at risk for spontaneous preterm birth (sPTB).Study design: This is a secondary analysis of a large study of magnesium for neuroprotection. Nonanomalous, singleton gestations complicated by preterm premature rupture of membranes (PPROM) or preterm labor (PTL) were included. Infants that developed CP were compared to controls that did not. The incidence of CP was stratified by GA groups. A logistic regression model was fit to adjust for confounders.Results: Of 1747 included pregnancies, 75 (4.3%) were affected by CP. Increasing GA at delivery was associated with lower rates of CP (RR 0.96, 95% CI 0.95-0.97; p<.0001). The most significant risk factor for CP was neonatal sepsis while the most significant protective factors were magnesium and antibiotic exposure. In the adjusted analysis, magnesium exposure (aRR 0.52, 95% CI 0.33-0.84; p = .007) and antibiotic exposure (aRR 0.52, 95% CI 0.28-0.95; p = .034) remained protective.Conclusion: The risk of CP among populations at high risk for sPTB decreases with advancing GA. While the majority of cases of CP occurred in children born <34 weeks, residual risk persisted thereafter. The effect of magnesium exposure is most pronounced before 28 weeks.