Cesarean Birth Tied to Higher Obesity Risk, Even Among Siblings

Troy Brown, RN

September 06, 2016

Children born by cesarean delivery were 15% more likely to become obese compared with those born vaginally, according to a new cohort study. Further, children born by cesarean delivery whose siblings were born vaginally were 64% more likely to become obese during follow-up compared with their siblings. The risk was slightly better for children born by vaginal birth after cesarean birth, as they had a 31% lower risk for offspring obesity compared with siblings born by repeat cesarean delivery.

"These findings suggest that this association may be a true adverse outcome of cesarean delivery that clinicians and patients should weigh when considering cesarean birth in the absence of a clear medical or obstetric indication," Jorge E. Chavarro, MD, ScD, from the Harvard T. H. Chan School of Public Health, Boston, Massachusetts and colleagues conclude. They report their findings in an article published online September 6 in JAMA Pediatrics.

Prior research has suggested a link between obesity in offspring and cesarean birth, but it has been unclear whether the association was the result of residual confounding. "To overcome these limitations, we investigated the association between cesarean birth and risk of obesity in offspring among participants of the Growing Up Today Study (GUTS), a large prospective cohort of individuals followed up from childhood through early adulthood," the authors write.

The study included 22,068 individuals born to 15,271 women. The researchers followed the children to age 20 to 28 years. A total of 4921 children (22.3%) of were born by cesarean delivery. For all children in the study, the cumulative obesity risk through the end of follow-up was 13%.

Women who underwent cesarean delivery were more likely to have, gestational diabetes, preeclampsia, pregnancy-induced hypertension, history of a previous cesarean delivery, and a higher prepregnancy body mass index.

Women with preterm and postterm births and offspring with either low birth weight or macrosomia were also more likely to have a cesarean delivery.

Cesarean rates were highest between 1985 and 1989, after which they decreased.

In unadjusted analyses, cesarean delivery was associated with a higher risk for obesity (risk ratio [RR], 1.30; 95% confidence interval [CI], 1.21 - 1.41; P < .001). The researchers then adjusted for potential confounders, including maternal age at delivery, race, region, year of birth, prepregnancy body mass index, maternal height, gestational diabetes, preeclampsia, pregnancy-induced hypertension, gestational age at delivery, birthweight, pregnancy smoking, previous cesarean delivery, offspring sex, and birth order.

After adjustment, the association was attenuated but still significant after adjustment, with a risk ratio of 1.15 (95% CI, 1.06 - 1.26; P = .002) compared with that for children born by vaginal delivery. Adjustment for prepregnancy body mass index was responsible for most of the attenuation.

Conclusions did not change after adjustment for breast-feeding duration (RR, 1.15; 95% CI, 1.05 - 1.26) and gestational weight gain (n = 11,067; RR, 1.10; 95% CI, 0.98 - 1.24).

The researchers then performed a within-family analysis of discordant modes of delivery, using data from successive pregnancies and siblings (n = 12,903 individuals with one or more siblings in GUTS) to minimize potential confounding by shared postnatal environment and time-invariant maternal factors. The odds of obesity were 64% (95% CI, 1.08 - 2.48; P = .02) higher among those born via cesarean delivery than among their siblings born via vaginal delivery. The association remained similar for individuals aged 9 to 18 years and for those aged 19 to 28 years.

Limitations of the study include lacking data on cesarean delivery indications and other labor and delivery details, as well as information on offspring microbiota or other potential biological factors that might elucidate the underlying mechanisms. The study suggests that babies exposed to their mother's vaginal and gastrointestinal microbiota may have a lower risk for obesity compared with babies born via cesarean delivery.

The authors have disclosed no relevant financial relationships.

JAMA Pediatr. Published online September 6, 2016. Abstract

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