Why women should wait to get pregnant after weight loss surgery

Babies born less than two years after their mothers have weight loss surgery may face a higher risk of serious complications than infants delivered after more time has passed, a U.S. study suggests.

Because obesity is linked to fertility issues, undergoing so-called bariatric surgery to shed excess weight can make it easier for some women to get pregnant. But when these women do conceive, they are more likely to have premature or small infants that require intensive care than women in the general population.

"Risks to the infant are highest in the first three years after an operation, and diminish over time," said lead study author Dr. Brodie Parent of the University of Washington in Seattle.

"This suggests that women should wait a minimum of three years after an operation before attempting conception," Parent added by email.

Globally, 1.9 billion adults are overweight or obese, according to the World Health Organization. In addition to its impact on fertility, obesity also increases the risk of heart disease, diabetes, joint disorders and certain cancers.

Bariatric surgery can be more effective for lasting weight loss than alternatives such as dieting or exercising, but it is not risk free. Like other surgery, there's a risk of infection, and weight-loss procedures can also lead to malnutrition.

For the current study, researchers wanted to see how the amount of time between bariatric surgery and pregnancy influences the risk of complications for babies.

They analyzed data from birth certificates and hospital records for 1,859 post-operative mothers and their babies, as well as for a control group of 8,437 randomly selected mothers that were similar in many ways but didn't have surgery. Records all came from Washington state and were collected from 1980 to 2013.

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Compared with infants born to women who didn't have surgery, babies born after mothers had bariatric procedures were 57 percent more likely to be premature, 25 percent more likely to be admitted to the neonatal intensive care unit (NICU) and 93 percent more likely to be small for their gestational age, researchers report in JAMA Surgery.

Timing appears to explain at least some of this added risk.

For women that had bariatric surgery, babies born less than two years afterwards were around 50 percent more likely to be premature, unusually small or spend time in the NICU than infants born at least four years later.

One limitation of the study is that researchers lacked data on what type of bariatric surgery women had, the authors note. Different procedures have varying effects on metabolism, hormonal balance and the odds of malnutrition, the authors point out.

Another drawback is that for many women in the study, researchers lacked data on weight or how many pounds were shed after surgery, making it possible that some complications linked to surgery might be connected to lingering obesity, the authors also explain.

The study also leaves a key question unanswered - whether obese women who have surgery wind up with a higher or lower risk for complications with their babies than they would have had without these operations, Dr. Aaron Dawes of the David Geffen School of Medicine at the University of California, Los Angeles, writes in an accompanying editorial.

Obesity alone puts women at risk for complications with their babies, Dawes told Reuters Health.

"We know that maintaining a healthy weight is important both to becoming pregnant and to delivering a healthy baby," Dawes added by email. "What we don't yet know is what the safest way is to achieve this weight and whether obese women who take steps to lose weight through surgery also put themselves and their children at risk."