Class Quetzal A, Rickert Martin E, Oberg Anna S, Sujan Ayesha C, Almqvist Catarina, Larsson Henrik, Lichtenstein Paul, D'Onofrio Brian M
Department of Obstetrics and Gynecology, University of Illinois, Chicago, Chicago, Illinois; the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana; and the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, and the Pediatric Allergy and Pulmonology Unit at Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden.
Obstet Gynecol. 2017 Dec;130(6):1304-1311. doi: 10.1097/AOG.0000000000002358.
To examine associations among interpregnancy interval, the duration from the preceding birth to the conception of the next-born index child, and adverse birth outcomes using designs that adjust for measured and unmeasured factors.
In this prospective cohort study, we used population-based Swedish registries from 1973 to 2009 to estimate the associations between interpregnancy interval (referent 18-23 months) and adverse birth outcomes (ie, preterm birth [less than 37 weeks of gestation], low birth weight [LBW; less than 2,500 g], small for gestational age [SGA; greater than 2 SDs below average weight for gestational age]). Analyses included cousin and sibling comparisons and postbirth intervals (ie, the interval between secondborn and thirdborn offspring predicting secondborn outcomes) to address unmeasured familial confounding.
Traditional cohort-wide analyses showed higher odds of preterm birth (adjusted odds ratio [OR] 1.51, 99% CI 1.39-1.63, 5.99% preterm births]) and LBW (adjusted OR 1.25, 99% CI 1.13-1.39, 3.32% LBW) after a short interpregnancy interval (0-5 months) compared with offspring born after an interpregnancy interval of 18-23 months (3.21% preterm births, 1.92% LBW). Except for preterm birth (adjusted OR 1.72, 99% CI 1.26-2.35), associations were attenuated in cousin comparisons. A small association between a short interpregnancy interval and preterm birth remained in sibling comparisons (adjusted OR 1.22, 99% CI 1.11-1.35), but associations with LBW (adjusted OR 0.83, 99% CI 0.74-0.94) and SGA (adjusted OR 0.74, 99% CI 0.64-0.85) reversed direction. For pregnancy intervals of 60 months or more, odds of preterm birth (adjusted OR 1.51, 99% CI 1.43-1.60, 5.07% preterm births), LBW (adjusted OR 1.61, 99% CI 1.50-1.73, 3.43% low-birth-weight births), and SGA (adjusted OR 1.54, 99% CI 1.42-1.66, 2.49% SGA births) were also higher when compared with the reference interval (1.53% SGA). Associations between long interpregnancy interval and adverse birth outcomes remained through cousin and sibling comparisons. Postbirth interval analyses showed familial confounding is present for short interpregnancy intervals, but supported independent associations for long interpregnancy intervals.
Familial confounding explains most of the association between a short interpregnancy interval and adverse birth outcomes, whereas associations with long interpregnancy intervals were independent of measured and unmeasured factors.
采用对测量因素和未测量因素进行校正的设计，研究妊娠间隔、前次分娩到本次出生索引儿童受孕的时间间隔与不良分娩结局之间的关联。
在这项前瞻性队列研究中，我们使用了1973年至2009年基于人群的瑞典登记数据，以估计妊娠间隔（参照组为18 - 23个月）与不良分娩结局（即早产[妊娠少于37周]、低出生体重[LBW；少于2500克]、小于胎龄儿[SGA；低于胎龄平均体重2个标准差以上]）之间的关联。分析包括堂兄弟姐妹和同胞比较以及产后间隔（即预测次胎结局的二胎和三胎后代之间的间隔），以解决未测量的家族性混杂因素。
传统的全队列分析显示，与妊娠间隔为18 - 23个月后出生的后代（早产率3.21%，低出生体重率1.92%）相比，妊娠间隔短（0 - 5个月）后早产（校正优势比[OR]1.51，99%CI 1.39 - 1.63，早产率5.99%）和低出生体重（校正OR 1.25，99%CI 1.13 - 1.39，低出生体重率3.32%）的几率更高。除早产外（校正OR 1.72，99%CI 1.26 - 2.35），堂兄弟姐妹比较中关联减弱。同胞比较中，妊娠间隔短与早产之间仍存在小的关联（校正OR 1.22，99%CI 1.11 - 1.35），但与低出生体重（校正OR 0.83，99%CI 0.74 - 0.94）和小于胎龄儿（校正OR 0.74，99%CI 0.64 - 0.85）的关联方向相反。对于妊娠间隔60个月或更长时间，与参照间隔（小于胎龄儿率1.53%）相比，早产（校正OR 1.51, 99%CI 1.43 - 1.60，早产率5.07%）、低出生体重（校正OR 1.61, 99%CI 1.50 - 1.73，低出生体重率3.43%）和小于胎龄儿（校正OR 1.54,99%CI 1.42 - 1.66，小于胎龄儿率2.49%）的几率也更高。妊娠间隔长与不良分娩结局之间的关联在堂兄弟姐妹和同胞比较中仍然存在。产后间隔分析显示，妊娠间隔短存在家族性混杂因素，但支持妊娠间隔长的独立关联。
家族性混杂因素解释了妊娠间隔短与不良分娩结局之间的大部分关联，而妊娠间隔长与不良分娩结局的关联独立于测量因素和未测量因素。
