Trends and correlates of self-reported alcohol and nicotine use among women before and during pregnancy, 2009–2017

•From 2009–2017, self-reported pre-pregnancy alcohol use increased.•Pre-pregnancy nicotine use and prenatal alcohol and nicotine use decreased.•Among pre-pregnancy users, frequent pre-pregnancy use increased odds of prenatal use.•Among pre-pregnancy users, socio-demographics were associated with prenatal use.•Prenatal substance use education prior to conception may reduce use in pregnancy To examine trends and correlates of frequency of self-reported alcohol and nicotine use among pregnant women. Cross-sectional study of 363,240 pregnancies from 2009 to 2017 screened for self-reported substance use at their first prenatal visit in Kaiser Permanente Northern California. Poisson regression with a log link function was used to estimate the annual prevalences of self-reported daily, weekly, and ≤ monthly alcohol and nicotine use, adjusting for socio-demographics. Generalized estimating equation models were used to estimate the adjusted odds ratios (aOR) of any self-reported prenatal alcohol or nicotine use among those who self-reported use in the year prior to pregnancy, by frequency of pre-pregnancy substance use and socio-demographics. The sample was 64 % non-White [mean (SD) age = 30.1 (5.6)]. From 2009–2017, alcohol use before pregnancy increased from 63.4%–65.9% (trend p-value = .008), and prenatal alcohol use decreased from 11.6%–8.8% (trend p-value