Associations of Prescription Opioid Use during Pregnancy with Low Birth Weight and Length of Hospital Stay: Analysis of PRAMS Data

Prescription opioid use among US pregnant women, primarily used for its analgesic properties, has increased substantially over the last decades. Findings from several studies investigating associations of prescription opioid use with adverse neonatal outcomes (including preterm birth, poor fetal growth, longer hospital stays, neonatal abstinence syndrome, and birth defects) were not consistent. We examined overall and infant-sex specific associations of maternal prescription opioid use in pregnancy with infant low birth weight and prolonged hospital stay.Methods: Data from the 2019-2020 Pregnancy Risk Assessment Monitoring System (PRAMS), a surveillance project of the CDC and state departments of health, was used for the analyses. Participants (N=35,404 mother-newborn pairs) with information on the exposure (maternal prenatal prescription opioid use) and outcomes (low infant birth weight defined as birth weight less than 2,500g, and, prolonged hospital stay defined as hospital stay longer than three days) were included in the analyses. We used crude and adjusted (for maternal age, race, household income, maternal smoking, depression, and infant sex) logistic regression models to estimate odds ratios (ORs) and corresponding 95% confidence intervals (CIs). We also evaluated infant sex as a potential effect modifier of the associations using stratified analyses and models with interaction terms. Results: Among study participants, 1,729 mothers (4.9%) reported prescription opioid use during pregnancy. Overall, 18.2% infants had low birth weight and 4.8% had prolonged hospital stay. In unadjusted models, mothers exposed to prescription opioids during pregnancy had 2-fold (95%CI:1.67-2.44) higher odds of delivering a low birth weight infant compared to mothers who were not exposed to prescription opioids during pregnancy. This association was attenuated but remained statistically significant after adjustment for all covariates (adjusted OR:1.70; 95%CI:1.40-2.07; p-value<0.01). We found no evidence of effect modification by infant sex (males: adjusted OR:1.65; 95%CI:1.25-2.18, and, females: adjusted OR:1.75; 95%CI:1.39-2.31) (interaction p-value>0.05). In unadjusted models, infants of mothers who reported prescription opioid use during pregnancy had 2.07-fold (95%CI:1.65-2.61) higher odds of prolonged hospital stay compared to infants of mothers who did not report prescription opioid use during pregnancy. This association remained statistically significant after adjustment for covariates (adjusted OR:1.86; 95% CI:1.47-2.36, p-value<0.01). We found no evidence of effect modification of this association by infant sex (males: adjusted OR:1.67; 95%CI:1.22-2.28, and females: adjusted OR:2.05; 95%CI:1.43-2.93) (interaction p-value>0.05). Conclusion: In the PRAMS cohort, prescription opioid use during pregnancy was associated with both low birth weight and prolonged hospital stay. We also found that the associations were similar among male and female infants. Our findings highlight the potential consequences of opioid use during pregnancy for further research.