Cesarean section without medical indication and risk of childhood asthma, and attenuation by breastfeeding

Background
Previous studies suggest that caesarean section (CS) may increase the risk of asthma in children, but none of them could preclude potential confounding effects of underlying medical indications for CS. We aim to assess the association between CS itself (without medical indications) and risk of childhood asthma.
Methods
We conducted a hospital-based case-control study on childhood asthma with 573 cases and 812 controls in Shanghai. Unconditional logistic regression models in SAS were employed to control for potential confounders.
Results
Our study found that CS without medical indication was significantly associated with elevated asthma risk (adjusted OR = 1.58 [95% CI 1.17–2.13]). However, this risk was attenuated in children fed by exclusive breastfeeding in the first six months after birth (adjusted OR = 1.39 [95% CI 0.92–2.10]). In contrast, the risk was more prominent in children with non-exclusive breastfeeding or bottle feeding (adjusted OR = 1.91 [95% CI 1.22–2.99]).
Conclusions
CS without medical indication was associated with an increased risk of childhood asthma. Exclusive breastfeeding in infancy may attenuate this risk.

研究背景
既往研究提示剖宫产（caesarean section, CS）可能增加儿童哮喘的发病风险，但所有研究均未能排除剖宫产潜在医学指征所带来的混杂效应。本研究旨在评估无医学指征剖宫产本身与儿童哮喘风险之间的关联。

研究方法
本研究以上海地区儿童哮喘为研究对象，开展基于医院的病例对照研究，共纳入573例病例与812例对照。采用SAS软件中的非条件logistic回归模型，对潜在混杂因素进行控制。

研究结果
本研究发现，无医学指征剖宫产与儿童哮喘风险升高存在显著相关性（校正后比值比OR=1.58，95%置信区间CI：1.17~2.13）。然而，出生后前6个月接受纯母乳喂养的儿童，该风险有所减弱（校正后OR=1.39，95%CI：0.92~2.10）。与之相反，非纯母乳喂养或奶瓶喂养的儿童，其哮喘升高风险更为显著（校正后OR=1.91，95%CI：1.22~2.99）。

研究结论
无医学指征剖宫产与儿童哮喘风险升高相关。婴儿期纯母乳喂养可削弱该风险关联。