Inter-pregnancy Weight Change and Risks of Severe Birth-Asphyxia-Related Outcomes in Singleton Infants Born at Term: A Nationwide Swedish Cohort Study

BackgroundMaternal overweight and obesity are associated with increased risks of birth-asphyxia-related outcomes, but the mechanisms are unclear. If a change of exposure (i.e., maternal body mass index [BMI]) over time influences risks, this would be consistent with a causal relationship between maternal BMI and offspring risks. Our objective was to investigate associations between changes in maternal BMI between consecutive pregnancies and risks of birth-asphyxia-related outcomes in the second offspring born at term.Methods and FindingsThis study was a prospective population-based cohort study that included 526,435 second-born term (≥37 wk) infants of mothers with two consecutive live singleton term births in Sweden between January 1992 and December 2012.We estimated associations between the difference in maternal BMI between the first and second pregnancy and risks of low Apgar score (0–6) at 5 min, neonatal seizures, and meconium aspiration in the second-born offspring. Odds ratios (ORs) were adjusted for BMI at first pregnancy, maternal height, maternal age at second delivery, smoking, education, mother´s country of birth, inter-pregnancy interval, and year of second delivery. Analyses were also stratified by BMI (2) in the first pregnancy.Risks of low Apgar score, neonatal seizures, and meconium aspiration increased with inter-pregnancy weight gain. Compared with offspring of mothers with stable weight (BMI change of −1 to 2), the adjusted OR for a low Apgar score in the offspring of mothers with a BMI change of 4 kg/m2 or more was 1.33 (95% CI 1.12–1.58). The corresponding risks for neonatal seizures and meconium aspiration were 1.42 (95% CI 1.00–2.02) and 1.78 (95% CI 1.19–2.68), respectively. The increased risk of neonatal seizures related to weight gain appeared to be restricted to mothers with BMI 2 in the first pregnancy. A study limitation was the lack of data on the effects of obstetric interventions and neonatal resuscitation efforts.ConclusionsRisks of birth-asphyxia-related outcomes increased with maternal weight gain between pregnancies. Preventing weight gain before and in between pregnancies may improve neonatal health.背景 母亲超重与肥胖与出生窒息相关不良结局的风险升高存在关联，但其具体致病机制尚未明确。若随时间变化的暴露因素（即母亲体质量指数（Body Mass Index, BMI））会对该风险产生影响，则可佐证母亲BMI与子代不良结局风险之间存在因果关系。本研究旨在探讨连续两次妊娠期间母亲BMI变化与足月出生的第二子代发生出生窒息相关不良结局的风险之间的关联。 方法与结果 本研究为一项基于人群的前瞻性队列研究，纳入了1992年1月至2012年12月间瑞典境内、母亲曾连续两次单胎足月活产的526435例足月（≥37周）第二子代婴儿。我们分析了首次与第二次妊娠期间母亲BMI差值与第二子代5分钟时低阿普加评分（Apgar score，0~6分）、新生儿惊厥及胎粪吸入综合征风险之间的关联。校正后的比值比（Odds Ratio, OR）已对首次妊娠时的BMI、母亲身高、第二次分娩时的母亲年龄、吸烟状态、受教育程度、母亲出生国家、妊娠间隔时长以及第二次分娩年份进行了校正。分析还按首次妊娠时的BMI（2）进行了分层。 结果显示，随着妊娠间期体重增加，子代出现低阿普加评分、新生儿惊厥及胎粪吸入综合征的风险均有所升高。与体重稳定（BMI变化范围为-1至2 kg/m²）的母亲所生子代相比，BMI增幅≥4 kg/m²的母亲所生子代出现低阿普加评分的校正OR为1.33（95%CI 1.12~1.58）；新生儿惊厥与胎粪吸入综合征的对应校正OR分别为1.42（95%CI 1.00~2.02）与1.78（95%CI 1.19~2.68）。与体重增加相关的新生儿惊厥风险升高似乎仅局限于首次妊娠时BMI为2的母亲。本研究的局限性在于缺乏产科干预措施与新生儿复苏操作相关影响的数据。 结论 妊娠间期母亲体重增加会升高子代出现出生窒息相关不良结局的风险。在孕前及妊娠间期预防体重增加，或可改善新生儿健康水平。