Children born via elective or emergency cesarean delivery may be at an increased risk for developing a food allergy, and children born very preterm were found to be at a lower risk for food allergy, according to a study published in the Journal of Allergy & Clinical Immunology.

Researchers conducted a longitudinal cohort study utilizing the Swedish Medical Birth Register as well as the National Patient Register to identify associations between perinatal characteristics and food allergy in children born between 2001 and 2012 (n = 1,232,739). Among these, 1,088,990 (88.3%) had complete data on all covariates: offspring sex, mode of delivery, gestational age, birth weight, and 5-minute Apgar score. Excluded from the study were patients who died or received a diagnosis of food allergy within the first 2 months of life. A total of 1,086,378 (88.1%) of children were included in the final study. Follow-up concluded with the first diagnosis of food allergy, death, or December 31, 2013. 

Maternal characteristics included age at delivery, country of birth, employment status, self-reported smoking habits as recorded at first antenatal visit, body mass index in early pregnancy, and maternal asthma/pulmonary disease. Methods of delivery were either vaginal or cesarean; cesarean was then divided into elective or emergency.

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Median age at first diagnosis of food allergy was 1.6 years; median follow-up was 6.4 years. Among the study participants, 26,732 (2.5%) had a diagnosed food allergy and, 14,534 (1.3%) received at least 2 hospital-based diagnoses. Female children, children born to Swedish mothers, and children whose mothers had asthma/pulmonary disease were more likely to have a diagnosed food allergy.

Associations were found between food allergy and cesarean delivery (hazard ratio [HR] 1.21]) for both elective (HR 1.18) and emergency (HR 1.24). Although food allergy was not associated with very preterm birth (HR 0.75), this negative association was not seen with moderately preterm (HR 0.96) or post-term (HR 1.01) birth. Future food allergy risk increased for children born large for gestational age (HR 1.15) and those with a low Apgar score (HR 1.22). Low birth weight or small for gestational age status did not affect future food allergy risk. The risk of food allergy in children born by cesarean delivery and having follow-up of ≥5 years was found to be 21% higher than those born by vaginal delivery (HR, 1.21).

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“It is noteworthy that our study suggests that both elective and emergency cesarean deliveries predispose to food allergies,” the authors stated. “This positive association strengthens the theory that exposure to vaginal microflora might reduce the risk of offspring atopic manifestations… Cesarean delivery seems to delay and alter the development of the offspring’s immune system, subsequently increasing the risk of atopic disease.”


Mitselou N, Hallberg J, Stephansson O, Almqvist C, Melén E, Ludvigsson JF. Cesarean delivery, preterm birth, and risk of food allergy: Nationwide Swedish cohort study of more than 1 million children [published online September 10, 2018]. J Allergy Clin Immunol. doi: 10.1016/j.jaci.2018.06.044