Nurse home visiting and prenatal substance use in a socioeconomically disadvantaged population in British Columbia: analysis of prenatal secondary outcomes in an ongoing randomized controlled trial

BACKGROUND: Nurse-Family Partnership (NFP) involves public health nurses providing frequent home visits from early pregnancy until children reach age 2 years, focusing on first-time parents experiencing socioeconomic disadvantage. Our aim was to evaluate NFP's effectiveness in improving child and maternal health. METHODS: We conducted an analysis of prenatal secondary outcomes in an ongoing randomized controlled trial in British Columbia; the data used in this analysis were collected from January 2014 to May 2017. Participants were pregnant girls and women aged 14-24 years who were preparing to parent for the first time and experiencing socioeconomic disadvantage. They were randomly allocated 1:1 to the intervention (NFP plus existing services) or control group (existing services). Prespecified prenatal secondary outcome indicators were changes in use of nicotine cigarettes and alcohol use by 34-36-weeks' gestation. We also report on prespecified exploratory cannabis and street drug use measures. We used mixed-effect models for longitudinal and clustered data to estimate intervention effects. Analyses were by intention to treat. RESULTS: The median gestational age at baseline for the 739 participants (368 participants in the intervention group, 371 in the comparison group) was 20 weeks, 6 days. By 34-36 weeks' gestation, NFP significantly reduced cigarette counts (over the past 2 d) (difference in changes [DIC] of count -1.6, 95% confidence interval [CI] -6.4 to -1.3) in those who smoked. NFP also significantly reduced rates of prenatal cannabis use (DIC -6.4, 95% CI -17.0 to -1.7), but not rates of street drug or "any" substance use. While we observed decreased rates of cigarette and alcohol use in both groups (DIC of proportions -2.8, 95% CI -15.3 to 0.6; DIC -0.5, 95% CI -8.7 to 1.8, respectively), these changes were not statistically significant. INTERPRETATION: We found no evidence that NFP was effective in reducing rates of prenatal cigarette and alcohol use; however, it led to reduced prenatal cannabis use, and in smokers it led to modest reductions in cigarette use. NFP may therefore hold promise for reducing some types of prenatal substance use in disadvantaged populations. Trial registration: ClinicalTrials.gov, no. NCT01672060.