Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, , Baltimore, Maryland, USA.
J Epidemiol Community Health. 2013 Dec 1;67(12):986-91. doi: 10.1136/jech-2013-202646. Epub 2013 Jul 19.
Studies in South Asia have documented increased risk of neonatal mortality among girls, despite evidence of a biological survival advantage. Associations between gender preference and mortality are cited as reasons for excess mortality among girls. This has not, however, been tested in statistical models.
A secondary analysis of data from a population-based randomised controlled trial of newborn infection prevention conducted in rural southern Nepal was used to estimate sex differences in early and late neonatal mortality, with girls as the reference group. The analysis investigated which underlying biological factors (immutable factors specific to the newborn or his/her mother) and environmental factors (mutable external factors) might explain observed sex differences in mortality.
Neonatal mortality was comparable by sex (Ref=girls; OR 1.06, 95% CI 0.92 to 1.22). When stratified by neonatal period, boys were at 20% (OR 1.20, 95% CI 1.02% to 1.42%) greater risk of early and girls at 43% (OR 0.70, 95% CI 0.51% to 0.94%) greater risk of late neonatal mortality. Biological factors, primarily respiratory depression and unconsciousness at birth, explained excess early neonatal mortality among boys. Increased late neonatal mortality among girls was explained by a three-way environmental interaction between ethnicity, sex and prior sibling composition (categorised as primiparous newborns, infants born to families with prior living boys or boys and girls, and infants born to families with only prior living girls).
Risk of neonatal mortality inverted between the early and late neonatal periods. Excess risk of early neonatal death among boys was consistent with biological expectations. Excess risk for late neonatal death among girls was not explained by overarching gender preference or preferential care-seeking for boys as hypothesised, but was driven by increased risk among Madeshi girls born to families with only prior girls.
南亚的研究表明，尽管女孩具有生物学上的生存优势，但她们的新生儿死亡率仍然较高。性别偏好与死亡率之间的关联被认为是导致女孩死亡率过高的原因之一。然而，这在统计模型中尚未得到验证。
本研究使用了尼泊尔南部农村地区一项针对新生儿感染预防的基于人群的随机对照试验的数据进行二次分析，以估计早期和晚期新生儿死亡率的性别差异，以女孩为参照组。该分析研究了哪些潜在的生物学因素（新生儿或其母亲特有的不可改变因素）和环境因素（可改变的外部因素）可以解释观察到的死亡率性别差异。
新生儿死亡率在性别间无差异（参照组为女孩；比值比 1.06，95%置信区间 0.92 至 1.22）。按新生儿期分层，男孩早期死亡的风险高 20%（比值比 1.20，95%置信区间 1.02%至 1.42%），女孩晚期死亡的风险高 43%（比值比 0.70，95%置信区间 0.51%至 0.94%）。生物学因素，主要是出生时的呼吸抑制和无意识，解释了男孩中早期新生儿死亡的超额风险。女孩中晚期新生儿死亡的增加由种族、性别和先前同胞组成之间的三向环境相互作用解释（分为初产妇新生儿、出生于有先前存活男孩或男孩和女孩的家庭的婴儿以及出生于仅有先前存活女孩的家庭的婴儿）。
新生儿死亡率在早期和晚期之间发生了逆转。男孩早期新生儿死亡风险增加与生物学预期一致。女孩晚期新生儿死亡风险增加不能用普遍的性别偏好或男孩优先寻求护理来解释，而是由仅生育女孩的家庭中出生的马德希女孩的风险增加所驱动。
