Unwanted pregnancies are associated with preterm birth, but not low birth weight.

Abstract

Background: Prior studies indicate that unintended and unwanted pregnancies can be associated with poor obstetric outcomes.

Objective: This study examined whether an unintended or unwanted pregnancy was associated with a preterm delivery and with low birth weight.

Study design: We conducted a secondary analysis of the 2017-19 cycle of the National Survey of Family Growth, a nationally-representative population- based survey of reproductive-aged people identifying as female in the United States. The sample consisted of respondents who had at least one prior live birth. Respondents were asked whether their most recent pregnancy was wanted (either at that time or prior to that time), unintended (wanted, but too soon, or unwanted at any time), or unwanted (did not want to be pregnant at any time). The primary outcomes were preterm delivery, defined as a live birth prior to 37 weeks' gestation, and low birth weight, defined as a birthweight less than 2500 grams. We also examined early preterm delivery (defined as a live birth prior to 34 weeks' gestation) as a secondary outcome, as well as restricting the sample to term deliveries only to examine low birth weight. We used chi square and Wilcoxon rank sum analysis for bivariable comparisons and logistic regression for multivariable models.

Results: Our sample consisted of 3,299 unique deliveries, 35.4% of which resulted from unintended pregnancies and 16.9% of which resulted from unwanted pregnancies. Overall, 12.7% of respondents had any preterm delivery, including 11.3% of those with intended pregnancies, 15.4% of those with unintended pregnancies (p = 0.02), 11.9% of those with wanted pregnancies and 16.9% of those with unwanted pregnancies (p = 0.01). Of the overall sample, 3.7% had a preterm delivery prior to 34 weeks gestation, including 3.0% of those with an intended pregnancy, 4.9% of those with an unintended pregnancy (p = 0.10), 3.1% of those with wanted pregnancies, and 6.3% of those with unwanted pregnancies (p = 0.01). Unwanted pregnancies remained associated with preterm delivery and early preterm delivery after adjusting for confounders (adjusted odds ratio 1.42, 95% confidence interval 1.02 - 1.98 for any preterm delivery, adjusted odds ratio 1.84, 95% confidence interval 1.10 - 3.08 for early preterm delivery). In our sample, 8.0% of respondents had a low birth weight neonate, including 6.6% of those with an intended pregnancy, 10.5% of those with an unintended pregnancy (p = 0.02), 7.4% of those with wanted and 10.5% of those with unwanted pregnancies (p = 0.10). These results were insignificant among those with term deliveries and after adjusting for confounders.

Conclusion: Unwanted pregnancies are associated with an increased risk of preterm delivery, but not low birth weight.