Examine the risk of preterm birth (PTB) among women who use drugs during pregnancy and have elevated α-fetoprotein (AFP).STUDY DESIGN:
The sample included California singleton live births in 2005 to 2010 contained within a hospital discharge database linked to the Prenatal Screening Program. A selection of mothers who did not use drugs was selected at a ratio of 4:1. Risk of PTB was calculated using adjusted odds ratios and 95% confidence intervals (CIs) for women who did or did not use drugs by their AFP percentile.RESULTS:
We identified 7190 women who used drugs and selected 28 760 women who did not. Of women using cocaine with AFP ≥95th percentile, 43.8% delivered prematurely. Women using drugs with AFP ≥95th percentile were 11 to 35 times as likely to deliver < 32 weeks.CONCLUSION:
The combination of drug use and elevated AFP results in high rates of PTB. This combination results in an additive risk.