结果：在13年的随访中，26732名儿童（2.5%）被诊断为食物过敏。食物过敏与剖腹产（HR，1.21；95% CI，1.18-1.25）、胎龄大（HR，1.15；95% CI，1.10-1.19）和新生儿5分钟Apgar评分低（HR，1.22；95% CI，1.10-1.36）呈正相关，但与极早产（妊娠<32周：HR，0.74；95% CI，0.56-0.98）呈负相关。未发现食物过敏与中度早产、低出生体重或小于胎龄之间存在关联。当结果仅限于2个诊断食物过敏记录时，风险估计是相似的。1000名接受剖腹产的儿童与对照组相比，额外5名儿童出现食物过敏，这表明通过剖宫产出生的儿童中17%的食物过敏可以通过这种方式（归因分数）来解释。
Cesarean delivery, preterm birth, and risk of food allergy: Nationwide Swedish cohort study of more than 1 million children
Background: Little is known about early-life risk factors for food allergy in children .
Methods: This nationwide Swedish cohort study of 1,086,378 children born in Sweden in 2001-2012 used prospectively recorded data from health care registers. Using Cox regression,we estimated hazard ratios (HRs) with 95% CIs for the association between perinatal characteristics (eg, cesarean delivery and preterm birth) and food allergy as defined by diagnoses in the National Patient Register, adjusting for infant sex and maternal factors (age at delivery, country of birth, parity, smoking, body mass index, and asthma/pulmonary disease).
Results: During the 13-year follow-up, 26,732 (2.5%) children were given a diagnosis of food allergy. Food allergy was positively associated with cesarean delivery (HR, 1.21; 95% CI, 1.18-1.25), large for gestational age (HR, 1.15; 95% CI,1.10-1.19), and low 5-minute Apgar score (HR, 1.22; 95% CI, 1.10-1.36) but negatively associated with very preterm birth (<32 weeks of gestation: HR, 0.74; 95% CI, 0.56-0.98). No association was found between food allergy and moderately preterm birth, low birth weight, or small for gestational age.Risk estimates were similar when the outcome was restricted to 2 records of diagnosed food allergy. In 1,000 children undergoing cesarean delivery, an extra 5 developed food allergy compared with the reference group, suggesting that 17% of food allergy in children born by means of cesarean delivery can be explained by this exposure (attributable fraction).
Conclusions: Cesarean delivery was associated with increasedrisk of food allergy, whereas very preterm birth decreased risk.
Department of Pediatrics, Orebro University € Hospital, S€ odra Grev Rosengatan, Orebro 701 85, Sweden
Niki Mitselou, Jenny Hallberg, Olof Stephansson, Catarina Almqvist, Erik Melen, and Jonas F. Ludvigsson