(Reuters Health) - Pregnant women who opt for surgical cesarean deliveries may be more likely than those who have vaginal deliveries to have a child that is overweight by its first birthday, a small study suggests.

For the analysis, researchers examined data on 727 infants born at two major hospitals in Singapore. Overall, 222 deliveries were surgical, and 74 of these procedures were elective - not done because of medical issues with the mother or baby. The rest were emergency surgeries.

By the time babies were 12 months old, about 12 percent of them were on the cusp of being overweight and about 2 percent were already overweight, the study found.

Women who had elective cesarean deliveries, also known as C-sections, were twice as likely to have overweight infants or babies on the cusp of becoming overweight compared to mothers who had vaginal deliveries.

“Only elective caesarean section is significantly associated with increased risk of early childhood obesity, while infants born via emergency caesarean section have a similar risk to that of infants born via vaginal delivery,” said senior study author Seng Bin Ang of KK Women’s and Children’s Hospital in Singapore.

“Many other studies have found that early childhood obesity has a tendency to persist into late childhood, adolescence and even adulthood,” Ang said by email.

While C-sections have long been linked to an increased risk of childhood obesity, the current study offers fresh evidence that the timing of the procedure and the reason behind it may influence the risk, Ang said.

In the study, researchers defined elective surgeries as procedures scheduled well in advance of delivery at women’s request or because of a previous C-section. They also counted surgeries scheduled more than 24 hours before delivery due to medical conditions that might make labor and delivery more complicated such as mothers with obesity or diabetes, or babies with serious health problems.

Emergency C-sections, by contrast, were scheduled within 24 hours of delivery to protect the health of the mother or infant because of situations like prolonged labor, fetal distress or a breech baby.

The connection between elective surgical deliveries and overweight babies persisted even after researchers accounted for a variety of other factors that might lead infants to become overweight, including mothers’ age, ethnicity, education, obesity, diabetes, high blood pressure or smoking.

Women also had a greater risk of overweight babies when the decision to deliver by C-section was made before the start of labor compared to when it was made after women went into labor.

One limitation of the study is that researchers lacked data on fathers, whose weight and health habits can independently influence weight in children, the study authors note.

It also wasn’t a controlled experiment designed to prove whether or how surgical deliveries or the timing of C-section decisions might directly impact the risk of overweight babies.

Even so, the results add to a large and growing body of evidence that children born by cesarean delivery are more likely to be heavy growing up than kids born by vaginal delivery, said the coauthor of an accompanying editorial, Dr. Jorge Chavarro of the Harvard TH Chan School of Public Health and Harvard Medical School in Boston.

“It is difficult to tell to what extent being overweight at 12 months means in terms of long-term weight trajectories and overall health,” Chavarro said by email. “However, previous studies have shown that the relation between cesarean delivery and childhood weight status seems to extend to older age groups including adolescents and young adults.”

SOURCE: bit.ly/2Pe0S1O and bit.ly/2KGIRIA JAMA Network Open, online November 21, 2018.