Maternal schizophrenia and adverse birth outcomes: what mediates the risk?

Purpose: Maternal schizophrenia is associated with adverse birth outcomes, but the reasons for this remain unclear. In a population-based cohort of infants born to women with schizophrenia, we determined the occurrence of key perinatal outcomes and explored whether factors identifiable in our datasets explained any elevated risk.

Methods: Using population-level health administrative data linked to clinical birth-registry data in Ontario, Canada (2006-2011), we examined the relative risk (RR) of preterm birth (< 37 weeks), small for gestational age (SGA), and Apgar scores < 8 in infants of women with schizophrenia (n = 4279) versus infants of unaffected women (n = 286,147). Generalized estimating equations determined whether reproductive history, maternal health conditions, pregnancy exposures, and complications explained elevated RRs.

Results: Among infants of women with schizophrenia, risk was higher for prematurity (11.4% vs. 6.9%, aRR 1.64, 95% CI 1.51-1.79), SGA (3.5% vs. 2.5%, aRR 1.40, 95% CI 1.20-1.64), and Apgar score < 8 at 1 (19.0% vs. 12.8%, aRR 1.49, 95% CI 1.40-1.59) and 5 min (5.6% vs. 3.0%, aRR 1.90, 95% CI 1.68-2.16). Smoking, fourfold more common among women with schizophrenia, was the variable that explained the greatest proportion of the elevated aRR for prematurity (9.9%), SGA (28.7%), and Apgar < 8 at 1 and 5 min (9.8%, 5.6%). Illicit substance use, certain reproductive history variables, and pregnancy complications also contributed to the elevated aRR for preterm birth.

Conclusions: Elevated risks of preterm birth, SGA, and low Apgar scores in infants of women with schizophrenia are partly explained by potentially modifiable factors such as smoking and illicit drug use, suggesting opportunities for targeted intervention.