Dosage Effect of Prenatal Home Visiting on Pregnancy Outcomes in At-Risk, First-Time Mothers

Abstract

In the United States, the current preterm birth rate is 12% or 500,000 infants annually. A home visiting program is one strategy to improve maternal-child health outcomes. An important aspect of home visiting is the duration of enrollment and the number of home visits, or a so-called “dosage effect.” The goal of this retrospective cohort study was to evaluate the effect of dosage of home visiting during the first and second trimesters on pregnancy outcomes. The dosage effect was assessed in at-risk, first-time mothers from 2007 to 2010. Eligible mothers had at least 1 risk characteristic: unmarried, low income, younger than 18 years, or suboptimal prenatal care. Outcomes were preterm birth and birth weight, that is, small for gestational age (SGA) versus appropriate or large for gestational age. The primary predictor was dosage of prenatal home visiting. Intensity of participation was measured as the number of completed prenatal home visits. From 2330 women, 918 prenatally enrolled first-time mothers had a singleton pregnancy; 441 enrolled by 26 weeks’ gestation and were included in the final cohort. Mean maternal age was 20 years, and mean gestational age at enrollment was 18.9 weeks. The preterm birth rate was 10.9%, and 17.9% of infants were SGA. The number of completed prenatal home visits ranged from 1 to 26, with fewer visits completed before 26 weeks (range, 1–16). In bivariate analyses, preterm birth was not significantly associated with gestational age at enrollment or number of home visits before 26 weeks. Compared with women delivering at full term, more women delivering preterm had a history of prior poor pregnancy outcome (25.0% vs 10.7%), hypertension/preeclampsia (27.1% vs 12.0%), and disorders of placentation (4.2% vs 0.5%), all P < 0.05. Women delivering an SGA infant did not differ significantly from women with non-SGA infants in mean gestational age at enrollment or number of total prenatal home visits. Timing of enrollment in home visiting was not independently associated with preterm birth, whereas the number of home visits before 26 weeks was statistically significant. Compared with the reference group of 3 home visits or less, completion of 8 or more home visits by 26 weeks was associated with an adjusted odds ratio of 0.38 for preterm birth (95% confidence interval [CI], 0.16–0.87). Compared with the reference group, having 12 or more prenatal home visits was significantly associated with a 0.32 hazard ratio of SGA status (95% CI, 0.15–0.68). Maternal age younger than 18 years was significantly associated with SGA status compared with age older than 18 years (hazard ratio, 1.37; 95% CI, 1.06–1.76). Given the importance of preterm birth to pediatric morbidity and health care costs, further conceptualization and measurements of prenatal provision of home visits are crucial. As prenatal programs expand for at-risk women, enrollment early in pregnancy and a high intensity of home visits during the first and second trimesters are important to achieve the goals of reducing preterm births and SGA status.