Maternal opioid use disorder and infant mortality in Wisconsin, United States, 2010-2018

OBJECTIVE

The difference in infant health outcomes by maternal opioid use disorder (OUD) status is understudied. We measured the association between maternal OUD during pregnancy and infant mortality and investigated whether this association differs by infant neonatal opioid withdrawal syndrome (NOWS) or maternal receipt of medication for OUD (MOUD) during pregnancy.

METHODS

We sampled 204,543 Medicaid-paid births from Wisconsin, United States (2010-2018). The primary exposure was any maternal OUD during pregnancy. We also stratified this exposure on NOWS diagnosis (no OUD; OUD without NOWS; OUD with NOWS) and on maternal MOUD receipt (no OUD; OUD without MOUD; OUD with <90 consecutive days of MOUD; OUD with 90+ consecutive days of MOUD). Our outcome was infant mortality (death at age <365 days). Demographic-adjusted logistic regressions measured associations with odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Maternal OUD was associated with increased odds of infant mortality (OR 1.43; 95% CI 1.02-2.02). After excluding infants who died <5 days post-birth (i.e., before the clinical presentation of NOWS), regression estimates of infant mortality did not significantly differ by NOWS diagnosis. Likewise, regression estimates did not significantly differ by maternal MOUD receipt in the full sample.

CONCLUSIONS

Maternal OUD is associated with an elevated risk of infant mortality without evidence of modification by NOWS nor by maternal MOUD treatment. Future research should investigate potential mechanisms linking maternal OUD, NOWS, MOUD treatment, and infant mortality to better inform clinical intervention.

Infant Mortality in Rural and Nonrural Counties in the United States

BACKGROUND AND OBJECTIVES

Rural counties have the highest infant mortality rates across the United States when compared with rates in more urban counties. We use a social-ecological framework to explain infant mortality disparities across the rural-urban continuum.

METHODS

We created a cohort of all births in the United States linked to infant death records for 2014 to 2016. Records were linked to county-level data from the Area Health Resources File and the American Community Survey and classified using the National Center for Health Statistics Urban-Rural Classification Scheme. Using multilevel generalized linear models, we investigated the association of infant mortality with county urban-rural classification, considering county health system resources and measures of socioeconomic advantage, net of individual-level characteristics, and controlling for US region and county centroid.

RESULTS

Infant mortality rates were highest in noncore (odds ratio [OR] = 1.32, 95% confidence interval [CI]: 1.26-1.39) and micropolitan counties (OR = 1.26, 95% CI: 1.20-1.32) when compared with large metropolitan fringe counties, controlling for geospatial measures. Inclusion of county health system characteristics did little to attenuate the greater odds of infant mortality in rural counties. Instead, a composite measure of county-level socioeconomic advantage was highly protective (adjusted OR = 0.84; 95% CI: 0.82-0.86) and eliminated any difference between the micropolitan and noncore counties and the large metropolitan fringe counties.

CONCLUSIONS

Higher infant mortality rates in rural counties are best explained by their greater socioeconomic disadvantage than more-limited access to health care or the greater prevalence of mothers' individual health risks.