Intermittent opioid use and ischemic placental disease: Study quantifies risks, raises questions.

Discomfort and, to a lesser extent, pain are common complaints during pregnancy, and some patients may turn to opioids for pain relief. Esposito and colleagues (Am J Epidemiol. 2021, in press) report associations between intermittent exposure to opioids during pregnancy and the risk of ischemic placental disease (IPD) - a syndrome that includes preeclampsia, placental abruption, small for gestational age (SGA) births, and preterm delivery. They found that early opioid exposure in pregnancy was associated with a modestly increased risk for abruption, SGA births, and preterm delivery, and both early and late exposure was associated with the greatest risk for these outcomes. Surprisingly, preeclampsia was not associated with opioid use. Through quantitative bias analysis, the authors cleverly tackle a number of biases to assess their roles in explaining the associations, including unmeasured confounding, outcome misclassification, and residual confounding; none exerted strong influences on the associations. Although the findings appear fairly robust on the surface, the lack of association between intermittent opioid use and preeclampsia, and important differences in characteristics of patients in the opioid exposed group compared to the unexposed group, suggest that further study is needed to clarify the relationship between intermittent opioid use, lifestyle factors, and IPD risk.