Importance Although high body mass index (BMI) is associated with adverse birth outcomes, the association with severe maternal morbidity is unclear. Objective To examine the association between prepregnancy BMI and severe maternal morbidity. Design, Setting, and Participants Retrospective population-based cohort study including all singleton hospital births in Washington State, 2004-2013. Demographic data and morbidity diagnoses were obtained from linked birth certificates and hospitalization files. Exposures Prepregnancy BMI (weight in kilograms divided by height in meters squared) categories included underweight (<18.5), normal BMI (18.5-24.9), overweight (25.0-29.9), obesity class 1 (30.0-34.9), obesity class 2 (35.0-39.9), and obesity class 3 (≥40). Main Outcomes and Measures Composite severe maternal morbidity or mortality included life-threatening conditions and conditions leading to serious sequelae (eg, amniotic fluid embolism, hysterectomy), complications requiring intensive care unit admission, and maternal death. Logistic regression was used to obtain adjusted odds ratios (ORs) and adjusted rate differences with 95% confidence intervals, adjusted for confounders (eg, maternal age and parity). Results Overall, 743 630 women were included in the study (mean age, 28.1 [SD, 6.0] years; 41.4% nulliparous). Prepregnancy BMI was distributed as follows: underweight, 3.2%; normal weight, 47.5%; overweight, 25.8%; obesity class 1, 13.1%; obesity class 2, 6.2%; and obesity class 3, 4.2%. Rates of severe maternal morbidity or mortality were 171.5, 143.2, 160.4, 167.9, 178.3 and 202.9 per 10 000 women, respectively. Adjusted ORs were 1.2 (95% CI, 1.0-1.3) for underweight women; 1.1 (95% CI, 1.1-1.2) for overweight women; 1.1 (95% CI, 1.1-1.2) for women with class 1 obesity; 1.2 (95% CI, 1.1-1.3) for women with class 2 obesity; and 1.4 (95% CI, 1.3-1.5) for women with class 3 obesity compared with women with normal BMI. Absolute risk increases (adjusted rate differences per 10 000 women, compared with women with normal BMI) were 28.8 (95% CI, 12.2-47.2) for underweight women, 17.6 (95% CI, 10.5-25.1) for overweight women, 24.9 (95% CI, 15.7-34.6) for women with class 1 obesity, 35.8 (95% CI, 23.1-49.5) for women with class 2 obesity, and 61.1 (95% CI, 44.8-78.9) for women with class 3 obesity. Conclusions and Relevance Among pregnant women in Washington State, low and high prepregnancy BMI, compared with normal BMI, were associated with a statistically significant but small absolute increase in severe maternal morbidity or mortality.

中文翻译：

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孕前体重指数与严重孕产妇发病率的关系

重要性 尽管高体重指数 (BMI) 与不良出生结局相关，但与严重孕产妇发病率的关联尚不清楚。目的 探讨孕前 BMI 与严重孕产妇发病率之间的关联。设计、设置和参与者 回顾性基于人群的队列研究，包括 2004-2013 年华盛顿州所有单胎医院分娩。人口统计数据和发病率诊断是从相关的出生证明和住院档案中获得的。暴露 孕前 BMI（体重（公斤）除以身高（米）的平方）类别包括体重不足（<18.5）、正常 BMI（18.5-24.9）、超重（25.0-29.9）、肥胖 1 级（30.0-34.9）、肥胖 2 级（ 35.0-39.9) 和肥胖 3 级 (≥40)。主要结果和措施 复合严重孕产妇发病率或死亡率包括危及生命的情况和导致严重后遗症的情况（例如，羊水栓塞、子宫切除术）、需要入住重症监护病房的并发症和孕产妇死亡。Logistic 回归用于获得调整后的优势比 (ORs) 和调整后的比率差异，具有 95% 置信区间，调整了混杂因素（例如，母亲的年龄和胎次）。结果 总体而言，研究中包括 743 630 名女性（平均年龄，28.1 [SD，6.0] 岁；41.4% 未生育）。孕前 BMI 分布如下：体重不足，3.2%；正常体重，47.5%；超重，25.8%；肥胖 1 级，13.1%；肥胖 2 级，6.2%；和肥胖 3 级，4.2%。严重孕产妇发病率或死亡率分别为 171.5、143.2、160.4、167.9、178.3 和 202。分别为每 10 000 名妇女 9 名。对于体重不足的女性，调整后的 OR 为 1.2（95% CI，1.0-1.3）；1.1 (95% CI, 1.1-1.2) 超重女性；1.1 (95% CI, 1.1-1.2) 对于 1 级肥胖女性；2 级肥胖女性为 1.2（95% CI，1.1-1.3）；与 BMI 正常的女性相比，3 级肥胖女性为 1.4（95% CI，1.3-1.5）。绝对风险增加（与体重指数正常的女性相比，每 10 000 名女性的调整率差异）对于体重不足的女性为 28.8（95% CI，12.2-47.2），对于超重女性为 17.6（95% CI，10.5-25.1），24.9（ 1 级肥胖女性为 95% CI，15.7-34.6），2 级肥胖女性为 35.8（95% CI，23.1-49.5），3 级肥胖女性为 61.1（95% CI，44.8-78.9）。结论和相关性 在华盛顿州的孕妇中，与正常 BMI 相比，低和高的孕前 BMI，