Goisis Alice, Remes Hanna, Barclay Kieron, Martikainen Pekka, Myrskylä Mikko
Department of Social Policy, London School of Economics and Political Science, London, United Kingdom.
Max Planck Institute for Demographic Research, Rostock, Germany.
Am J Epidemiol. 2017 Dec 1;186(11):1219-1226. doi: 10.1093/aje/kwx177.
Advanced maternal age at birth is considered a major risk factor for birth outcomes. It is unclear to what extent this association is confounded by maternal characteristics. To test whether advanced maternal age at birth independently increases the risk of low birth weight (<2,500 g) and preterm birth (<37 weeks' gestation), we compared between-family models (children born to different mothers at different ages) with within-family models (children born to the same mother at different ages). The latter procedure reduces confounding by unobserved parental characteristics that are shared by siblings. We used Finnish population registers, including 124,098 children born during 1987-2000. When compared with maternal ages 25-29 years in between-family models, maternal ages of 35-39 years and ≥40 years were associated with percentage increases of 1.1 points (95% confidence intervals: 0.8, 1.4) and 2.2 points (95% confidence intervals: 1.4, 2.9), respectively, in the probability of low birth weight. The associations are similar for the risk of preterm delivery. In within-family models, the relationship between advanced maternal age and low birth weight or preterm birth is statistically and substantively negligible. In Finland, advanced maternal age is not independently associated with the risk of low birth weight or preterm delivery among mothers who have had at least 2 live births.
出生时母亲年龄较大被认为是影响分娩结局的一个主要风险因素。目前尚不清楚这种关联在多大程度上受到母亲特征的混杂影响。为了检验出生时母亲年龄较大是否会独立增加低出生体重（<2500克）和早产（<37周妊娠）的风险，我们比较了家庭间模型（不同年龄的不同母亲所生子女）和家庭内模型（同一母亲在不同年龄所生子女）。后一种方法减少了兄弟姐妹共有的未观察到的父母特征所造成的混杂影响。我们使用了芬兰人口登记数据，其中包括1987年至2000年期间出生的124,098名儿童。在家庭间模型中，与母亲年龄在25至29岁的情况相比，母亲年龄在35至39岁和≥40岁时，低出生体重概率分别增加了1.1个百分点（95%置信区间：0.8，1.4）和2.2个百分点（95%置信区间：1.4，2.9）。早产风险的关联情况类似。在家庭内模型中，母亲年龄较大与低出生体重或早产之间的关系在统计学上和实质上都可忽略不计。在芬兰，对于至少生育过2个存活子女的母亲，母亲年龄较大与低出生体重或早产风险并无独立关联。
