Objectives <p>Overdoses are a leading cause of maternal mortality in the US, but limited evidence exists about patterns of nonfatal overdose, a key risk factor for subsequent fatal overdose, or of other drug-related harms. Here, we estimate prevalences of nonfatal overdose and injection-related endocarditis and abscesses/cellulitis across the 21 months spanning pregnancy and the postpartum year.</p> Methods <p>Among people who experienced an in-hospital birth in New York State between 9/1/2016 and 1/1/2018 (<i>N</i> = 330,872), we estimated the prevalences of hospital-based diagnoses of nonfatal overdose and of injection-related bacterial infections (i.e., endocarditis, abscesses, and cellulitis) across these 21 months; by trimester and postpartum quarter; and by social position (e.g., race/ethnicity, rurality, payor).</p> Results <p>The 21-month nonfatal overdose prevalence was 158/100,000 births (CI: 145/100,000, 172/100,000); the 21-month prevalence of injection-related bacterial infections was 56/100,000 births (CI: 49/100,000, 65/100,000). There was a trend such that rates of overdose and of injection-related bacterial infections declined as pregnancy progressed and rebounded postpartum. Rates of all outcomes were highest outside of large metropolitan areas and among publicly insured residents.</p> Conclusions for Practice <p>The trend toward diminished rates during pregnancy is supported by past qualitative studies. If confirmed by future research in other geographical regions and with larger sample sizes, this finding holds promise for programmatic and policy interventions. Interventions co-designed with people who use drugs could complement and support harm reduction efforts that pregnant people are already engaging in independently. Such efforts can help people who use drugs survive the pregnancy and postpartum year.</p>