title: Risk of preterm birth among women using drugs during pregnancy with elevated α-fetoprotein.
abstract: Examine the risk of preterm birth (PTB) among women who use drugs during pregnancy and have elevated α-fetoprotein (AFP).
  
  
  
  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.
  
  
  
  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.
  
  
  
  The combination of drug use and elevated AFP results in high rates of PTB. This combination results in an additive risk.
authors.affiliation: Department of Pediatrics, University of California, San Diego, La Jolla, CA, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Baer
authors.affiliation: Department of Pediatrics, University of California, San Diego, La Jolla, CA, USA.
authors.forename: C D
authors.initials: CD
authors.lastname: Chambers
authors.affiliation: Department of Epidemiology and Pediatrics, University of Iowa, Iowa City, IA, USA.
authors.forename: K K
authors.initials: KK
authors.lastname: Ryckman
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA.
authors.forename: S P
authors.initials: SP
authors.lastname: Oltman
authors.affiliation: Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, CA, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: Norton
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA.
authors.forename: L L
authors.initials: LL
authors.lastname: Jelliffe-Pawlowski
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000097:blood; D002140:California / Q000453:epidemiology; D005260:Female; D006801:Humans; D016015:Logistic Models; D011247:Pregnancy; D047928:Premature Birth / Q000139:chemically induced / Q000453:epidemiology*; D011296:Prenatal Diagnosis / Q000379:methods*; D018570:Risk Assessment; D012307:Risk Factors; D019966:Substance-Related Disorders / Q000097:blood*; D055815:Young Adult; D000509:alpha-Fetoproteins / Q000032:analysis*
chemical_list: D015415:Biomarkers; D000509:alpha-Fetoproteins