ObjectiveMothers whose newborn experiences adversity may neglect their own health to care for their affected infant or following a perinatal death. Weight gain after pregnancy is one measure of maternal self‐care. We measured interpregnancy weight gain among women whose child had an adverse perinatal event.MethodsThis population‐based observational study included 192 154 primigravid women with two consecutive singleton births in Ontario, Canada. Outcomes included net weight gain, and adjusted odds ratios (aOR) of moving to a higher body mass index (BMI) category between pregnancies, comparing women whose child did versus did not experience either a perinatal death, prematurity, severe neonatal morbidity, major congenital anomaly, or severe neurologic impairment.ResultsPerinatal death was associated with a +3.5 kg (95% confidence interval [CI]: 2.1–4.9) net higher maternal weight gain in the subsequent pregnancy. Relative to term births, preterm birth <32 weeks (+3.2 kg, 95% CI: 1.9–4.6), 32–33 weeks (+1.8 kg, 95% CI: 0.7–2.8) and 34–36 weeks (+0.9 kg, 95% CI: 0.6–1.3) were associated with higher net weight gain. Having an infant with severe neonatal morbidity was associated with a +1.2 kg (95% CI: 0.3–2.1) weight gain. Likewise, the aOR of moving to a higher BMI category was 1.27 (95% CI, 1.14–1.42) following a perinatal death, 1.21 (95% CI: 1.04–1.41) after a preterm birth <32 weeks, and 1.11 (95% CI: 1.02–1.22) with severe neonatal morbidity.ConclusionGreater interpregnancy weight gain, and movement to a higher BMI category, are each more likely in a woman whose first‐born was affected by certain major adverse perinatal events.