Neighborhood Income Mobility and Risk of Neonatal and Maternal Morbidity.

Importance: Residing in a low-income neighborhood is generally associated with worse pregnancy outcomes. It is not known if moving from a low- to higher-income area between 2 pregnancies alters the risk of adverse birth outcomes in the subsequent birth compared with women who remain in low-income areas for both births. Objective: To compare the risk of adverse maternal and newborn outcomes among women who achieved upward area-level income mobility vs those who did not. Design, Setting, and Participants: This population-based cohort study was completed in Ontario, Canada, from 2002 to 2019, where there is universal health care. Included were all nulliparous women with a first-time singleton birth at 20 to 42 weeks' gestation, each residing in a low-income urban neighborhood at the time of the first birth. All women were then assessed at their second birth. Statistical analysis was conducted from August 2022 to April 2023. Exposure: Movement from a lowest-income quintile (Q1) neighborhood to any higher-income quintile neighborhood (Q2-Q5) between the first and second birth. Main Outcomes and Measures: The maternal outcome was severe maternal morbidity or mortality (SMM-M) at the second birth hospitalization or up to 42 days post partum. The primary perinatal outcome was severe neonatal morbidity or mortality (SNM-M) within 27 days of the second birth. Relative risks (aRR) and absolute risk differences (aARD) were estimated by adjusting for maternal and infant characteristics. Results: A total of 42 208 (44.1%) women (mean [SD] age at second birth, 30.0 [5.2] years) experienced upward area-level income mobility, and 53 409 (55.9%) women (age at second birth, 29.0 [5.4] years) remained in income Q1 between births. Relative to women who remained in income Q1 between births, those with upward mobility had a lower associated risk of SMM-M (12.0 vs 13.3 per 1000 births), with an aRR of 0.86 (95% CI, 0.78 to 0.93) and aARD of -2.09 per 1000 (95% CI, -3.1 to -0.9 per 1000 ). Likewise, their newborns experienced lower respective rates of SNM-M (48.0 vs 50.9 per 1000 live births), with an aRR of 0.91 (95% CI, 0.87 to 0.95) and aARD of -4.7 per 1000 (95% CI, -6.8 to -2.6 per 1000). Conclusions and Relevance: In this cohort study of nulliparous women living in low-income areas, those who moved to a higher-income area between births experienced less morbidity and death in their second pregnancy, as did their newborns, compared with those who remained in low-income areas between births. Research is needed to determine whether financial incentives or enhancement of neighborhood factors can reduce adverse maternal and perinatal outcomes.