Background Epidemiological studies have reported conflicting results in the association between Caesarean section (CS) birth and childhood obesity. Many of these studies had small sample sizes, were unable to distinguish between elective/planned and emergency CS, and did not adjust for the key confounder maternal pre-pregnancy body mass index (BMI). We investigated the association between CS delivery, particularly elective/planned and childhood obesity, using the Growing Up in New Zealand prospective longitudinal cohort study.
Methods Pregnant women planning to deliver their babies on the New Zealand upper North Island were invited to participate. Mode of delivery was categorised into spontaneous vaginal delivery (VD) (reference), assisted VD, planned CS and emergency CS. The main outcome was childhood obesity defined according to the International Obesity Taskforce criteria at age 24 and 54 months. Multinomial logistic regression and mixed-effects linear regression models were fitted with associations adjusted for several potential confounders.
Results Of the 6599 infants, 1532 (23.2%) were delivered by CS. At age 24 months, 478 (9.3%) children were obese. There was a statistically significant association between planned CS adjusted relative risk ratio (aRRR=1.59; (95% CI 1.09 to 2.33)) and obesity but not for emergency CS (aRRR=1.27; (95% CI 0.89 to 1.82)). At age 54 months there was no association between planned CS (aRRR=0.89; (95% CI 0.54 to 1.45)) and obesity as well as for emergency CS (aRRR=1.19; (95% CI 0.80 to 1.77)). At all-time points those born by planned CS had a higher mean BMI (adjusted mean difference=0.16; (95% CI 0.00 to 0.31), p=0.046).
Conclusions Planned CS was an independent predictor of obesity in early childhood. This suggests that birth mode influences growth, at least in the short term. This association occurred during a critical phase of human development, the first 2 years of life, and if causal might result in long-term detrimental cardiometabolic changes.
- caesarean section
- vaginal microflora, obesity
- New Zealand
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Contributors GM, FPM, JR, PNB, LCK, SMBM, ASK conceived and designed the study. SM is the Principal Investigator of the GUiNZ study. GM analysed the data and all authors interpreted the results. GM wrote the first draft of the article and FPM, JR, PNB, LCK, SMBM, ASK revised it critically for important intellectual content. All authors approved the final version.
Funding The Growing Up in New Zealand study was supported by The University of Auckland; the Ministry of Social Development; the Ministry of Health; the Ministry of Research, Science, and Technology; the Health Research Council of New Zealand; the Ministry of Justice; the Families Commission; the Children’s Commission; the Department of Labour; the Ministry of Education; Housing New Zealand; and Sport and Recreation New Zealand. GM is supported by the Irish Centre for Fetal and Neonatal Translational Research (INFANT) (grant no. 12/RC/2272).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Ethics approval was granted by the Northern Y Regional Ethics Committee (ethics number—NTY/08/06/055) and all guardians of cohort participants provided written informed consent.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data may be obtained from a third party and are not publicly available.