Unintended pregnancy: Risk factors and perinatal outcomes in a nulliparous population

Previous studies have found that unintended pregnancies are associated with late prenatal care and adverse pregnancy outcomes. Unintended pregnancy in nulliparous individuals who establish early prenatal care is of particular interest because outcomes in these pregnancies are not confounded by outcomes from prior births or late initiation of prenatal care.

The purpose of this study is to investigate maternal risk factors and perinatal outcomes associated with unintended pregnancies in a nulliparous population who established early prenatal care.

This is a secondary analysis of the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be (nuMoM2b), a prospective cohort study in which 10,038 nulliparous individuals were followed throughout their pregnancy from the first trimester. Participants who indicated their pregnancy intention on a standardized questionnaire were included in the analysis. Maternal characteristics and pregnancy outcomes of those reporting a planned pregnancy were compared with those reporting an unplanned pregnancy. Multivariable logistic regression with stepwise model selection was used to identify maternal characteristics associated with unplanned pregnancy.

A total of 10,020 participants in the nuMoM2b study identified their pregnancies as either "planned" (58.5%, n = 5,859) or "unplanned" (41.5%, n = 4161). Compared with those having a planned pregnancy, those with unplanned pregnancies were more likely to be younger, non-Hispanic Black or Asian, not married, of lower socioeconomic status, and to report alcohol or tobacco use prior to pregnancy, even after adjusting for covariates (all p values ≤ 0.04). Those with unplanned pregnancies were not more likely to have a history of mental illness. After controlling for potentially confounding factors, only treatment of mental illness during pregnancy or postpartum remained significantly associated with unplanned pregnancy (adjusted odds ratio 1.29, 95% confidence interval 1.01-1.64, p = 0.04).

Our findings suggest that nulliparas who received early prenatal care for an unplanned pregnancy did not have more frequent adverse perinatal outcomes compared to planned pregnancies; however, they received treatment more frequently for mental illness during pregnancy and postpartum.