Elective Cesarean Doubles Risk of Overweight Infant

Becky McCall

November 27, 2018

Elective cesarean delivery is associated with the resulting child having an increased risk of or being overweight at age 12 months, according to a prospective birth cohort study that looked at outcomes of elective and emergency cesarean sections separately.

The prevalences of being at risk of or being overweight for children aged 12 months born by elective cesarean section were 12.2% and 2.3% of total births, respectively, to give an adjusted odds ratio (OR) of 2.02 for both outcomes combined.

In contrast, no significant associations were found between overweight and emergency cesarean delivery.

"Our main findings revealed disparate associations of elective and emergency cesarean deliveries with early childhood overweight," write the authors, led by Meijin Cai, BSc, from Duke-NUS Medical School, Singapore, in their article published online November 21 in JAMA Network Open.

"Choice of delivery mode may influence risk of early childhood overweight. Clinicians are encouraged to discuss potential long-term implications of elective cesarean delivery on child metabolic outcomes with patients who intend to have children," they add, noting the importance of understanding the association when rates of elective cesarean sections are rising globally.

The few known existing studies that have examined cesarean section subgroups separately have similarly found an increased risk of overweight for elective cesarean delivery for older children aged 3 to 7 years, the authors highlight. Until now, none have looked at the association with early childhood overweight.

Caroline Mitchell, MD, Harvard Medical School, Boston, Massachusetts, and Jorge E. Chavarro, MD, Harvard School of Public Health, wrote an invited commentary accompanying the study.

They note the growing number of studies that have found an association between cesarean delivery and childhood obesity. And, with reference to the study led by Cai and colleagues, they point out that "separating elective procedures performed before the onset of labor from other cesarean deliveries can also provide insights into one of the proposed mechanisms underlying this association: differences in infant gut microbiome resulting from differences in exposure to maternal vaginal secretions."

They add that the study is "undoubtedly an important piece for solving the cesarean delivery–childhood obesity puzzle."

But they add it highlights the fact that methodological issues make it difficult to understand what it means to be exposed to a cesarean delivery.

"There is a wide spectrum between clearly elective cesarean procedures and unmistakably emergency interventions...Correctly defining exposure is necessary for interpreting the clinical impact of study results."

Overweight Risk Differs Depending on Type of Cesarean Section

The researchers hypothesized that infants born by elective cesarean section versus emergency cesarean may differ in risk of overweight during early childhood.

Data were drawn from a multiethnic Asian population enrolled in the ongoing Growing Up in Singapore Towards Healthy Outcomes (GUSTO) prospective mother–child birth cohort study. A total of 1237 pregnant women in their first trimester were enrolled.

Elective cesarean delivery was defined as a result of advanced planning because of, for example, maternal request, history of cesarean delivery, or maternal obesity.

Emergency cesarean section was defined as unplanned and/or a decision made during the 24 hours before delivery because of deteriorating maternal or fetal health. Vaginal delivery was the reference.

Infant weight and length were measured at 12 months using World Health Organization 2006 child growth standards, and these were used to compute nonethnic-specific body mass index (BMI) for age z scores. High BMI status at risk of overweight was defined as a z score of between 1 standard deviation (SD) and ≤ 2 SDs. Overweight was defined as a z score of > 2 SDs.

Of the 727 single births analyzed, 30.5% were by cesarean section and 10.2% were elective (33.3% of total cesarean delivery births).

The emergency cesarean delivery rate was 19.8%, or 64.9% of total cesarean section births.

Elective cesarean section delivery had twice the risk of overweight or being overweight in the child at 12 months of age, a significant association with an OR of 2.05 (P = .03) compared with vaginal delivery, adjusted for maternal ethnicity, age at delivery, educational level, parity, early pregnancy BMI, antenatal active or passive smoking, hypertensive disorders of pregnancy, gestational diabetes, and infant sex-adjusted body weight for gestational age.

After additional adjustment for intrapartum antibiotics and infant feeding during the first 6 months, two known mediators of childhood overweight/obesity, the OR was 2.02 (P = .04).

In conclusion, the commentators point out that repeated surgical procedures are one of the primary drivers of high cesarean section rates, and if cesarean birth after labor — as happens in an emergency cesarean section — is protective for obesity, "this could encourage more physicians to offer women attempted vaginal delivery after a cesarean delivery [so-called vaginal birth after cesarean (VBAC)]."

"However, if any cesarean birth (prelabor or postlabor) is associated with obesity, then avoiding the first cesarean birth should be the priority," the commentators add.

Mitchell and Chavarro say, "Better definitions of both exposure and outcome are necessary to be sure that results can be compared across studies."

"Only then will we be able to decipher whether this consistent association is causal, and also how we should address it."

Cai has reported no relevant financial relationships. Chavarro has reported receiving grants from the National Institutes of Health.

JAMA Netw Open. Published online November 21, 2018. Full text, Commentary

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