Individuals born by caesarean delivery were 15% more likely to become obese as children than individuals born by vaginal birth – the increased risk may persist through adulthood, according to a large new study from Harvard TH Chan School of Public Health.
In addition, individuals born via caesarean delivery were 64% more likely to be obese than their siblings born by vaginal birth.
The researchers also found that individuals born via vaginal birth among women who had undergone a previous caesarean delivery were 31% less likely to become obese compared with those born via caesarean birth following a caesarean birth. “Caesarean deliveries are without a doubt a necessary and lifesaving procedure in many cases,” said Jorge Chavarro, associate professor of nutrition and epidemiology at Harvard Chan School and senior author of the study. “But caesareans also have some known risks to the mother and the newborn. Our findings show that risk of obesity in the offspring could another factor to consider.”
Nearly 1.3m caesareans are performed each year in the US, accounting for one third of all deliveries. While a number of previous studies have suggested a link between caesarean delivery and a higher risk of obesity in offspring, the studies were either too small to detect a clear association or lacked detailed data.
The new analysis included 16 years’ worth of data from more than 22,000 young adults in the Growing Up Today Study (GUTS), in which participants answered survey questions every year or two years from 1996-2012. The researchers looked at the participants’ body mass index (BMI) over time; at whether or not they were delivered via caesarean (using information collected from participants’ mothers, participants in the Nurses’ Health Study II); and at other factors that could play a role in obesity, such as the mothers’ pre-pregnancy BMI, smoking status, age at delivery, and where they lived. They also looked at whether the mothers had previous caesarean deliveries.
“I think that our findings – particularly those that show a dramatic difference in obesity risk between those born via caesarean and their siblings born through vaginal delivery – provide very compelling evidence that the association between caesarean birth and childhood obesity is real,” said Chavarro. “That’s because, in the case of siblings, many of the factors that could potentially be playing a role in obesity risk, including genetics, would be largely the same for each sibling – except for the type of delivery.”
Importance: Cesarean birth has been associated with higher risk of obesity in offspring, but previous studies have focused primarily on childhood obesity and have been hampered by limited control for confounders.
Objective: To investigate the association between cesarean birth and risk of obesity in offspring.
Design, Setting, and Participants: A prospective cohort study was conducted from September 1, 1996, to December 31, 2012, among participants of the Growing Up Today Study, including 22 068 offspring born to 15 271 women, followed up via questionnaire from ages 9 to 14 through ages 20 to 28 years. Data analysis was conducted from October 10, 2015, to June 14, 2016.
Exposure: Birth by cesarean delivery.
Main Outcomes and Measures: Risk of obesity based on International Obesity Task Force or World Health Organization body mass index cutoffs, depending on age. Secondary outcomes included risks of obesity associated with changes in mode of delivery and differences in risk between siblings whose modes of birth were discordant.
Results: Of the 22 068 offspring (20 950 white; 9359 male and 12 709 female), 4921 individuals (22.3%) were born by cesarean delivery. The cumulative risk of obesity through the end of follow-up was 13% among all participants. The adjusted risk ratio for obesity among offspring delivered via cesarean birth vs those delivered via vaginal birth was 1.15 (95% CI, 1.06-1.26; P = .002). This association was stronger among women without known indications for cesarean delivery (adjusted risk ratio, 1.30; 95% CI, 1.09-1.54; P = .004). Offspring delivered via vaginal birth among women who had undergone a previous cesarean delivery had a 31% (95% CI, 17%-47%) lower risk of obesity compared with those born to women with repeated cesarean deliveries. In within-family analysis, individuals born by cesarean delivery had 64% (8%-148%) higher odds of obesity than did their siblings born via vaginal delivery.
Conclusions and Relevance: Cesarean birth was associated with offspring obesity after accounting for major confounding factors. Although additional research is needed to clarify the mechanisms underlying this association, clinicians and patients should weigh this risk when considering cesarean delivery in the absence of a clear indication.
Changzheng Yuan; Audrey J Gaskins; Arianna I Blaine; Cuilin Zhang; Matthew W Gillman; Stacey A Missmer; Alison E Field; Jorge E Chavarro