The findings are part of an evidence review that was led by Melinda A. Maggard, M.D., of the University of California at Los Angeles and the RAND Corporation in Santa Monica, CA, and performed by AHRQ's Southern California Evidence-Based Practice Center at RAND. The review was based on findings from 75 studies, including three that compared pregnancies of non-obese women to those of obese women as well as to pregnancies of women who lost weight surgically. The evidence review was conducted at the request of the American College of Obstetricians and Gynecologists.

In one study of laparoscopic gastric banding, a type of bariatric surgery, the authors found that none of the women who underwent surgery developed gestational diabetes or high blood pressure during their pregnancies. By comparison, 22 percent of obese pregnant women developed diabetes and 3 percent developed high blood pressure in the same study. Thirteen other studies supported these findings. Neonatal outcomes, like preterm delivery, low birth weight, and high birth weight, were also likely to be better in pregnancies of women following bariatric surgery than in pregnancies of obese women.

"Women of childbearing age who are considering weight-loss surgery should talk to their doctors about the implications for the future," said AHRQ Director Carolyn M. Clancy, M.D. "While we don't have all the answers yet, these preliminary findings may help physicians guide their patients. "

More than 50,000 women a year ages 18 to 45 undergo bariatric surgery procedures that include gastric bypass surgery, vertical-banded gastroplasty, and other inpatient weight-reduction procedures. Others have outpatient laparoscopic adjustable gastric banding procedures.

Dr. Maggard said, "Although no randomized controlled trials were found that specifically assessed pregnancy outcomes following surgery, the existing body of evidence revealed that, in general, some maternal and neonatal complications appear lower in pregnancies following bariatric surgery as compared to pregnancies in obese women." Dr. Maggard added that their rates even approach those seen in pregnancies in non-obese women.

The evidence report also found that:

Nutritional problems during pregnancy following two types of bariatric surgeries, gastric bypass and laparoscopic gastric band procedures, appear to be uncommon and may result from not following instructions for taking supplements. Nutritional problems appear to be more frequent and severe in mothers who undergo another bariatric surgical procedure, biliopancreatic diversion surgery. There is not enough evidence to determine if having bariatric surgery affects the likelihood of needing a cesarean section to give birth. There is some evidence to guide a woman's decision as to how long she should wait after having bariatric surgery to become pregnant. The typical recommended time period is 1 year, which usually coincides with the period of most rapid weight loss. The effects of bariatric surgery on a woman's fertility have not been well studied. Studies including a small number of patients report possible improvement in the ability to conceive and deliver a child following bariatric surgery. These results, along with reports of normalization of sex hormones and menstrual irregularities, as well as improvement in polycystic ovary syndrome -- a health problem that can affect a woman's ability to have children -- following surgery suggest that fertility may improve. These findings are consistent with those observed in formerly obese women after non-surgically induced weight loss. Adverse events following bariatric surgery are probably uncommon; their true incidence is not known and case reports tend to be the main source to date capturing such events. Bowel obstruction, which is most commonly due to internal hernia, is the more frequently reported surgical complication in pregnant women following bariatric surgery procedures. Deaths of mothers and fetuses have been reported in some of these cases. Of note, bowel obstruction also occurs in bariatric surgery patients who do not become pregnant. There is no evidence about whether oral contraceptive pills are as effective in women following bariatric surgery as they are in women in general. There is a need for research on this subject

Details are in "Pregnancy and Fertility following Bariatric Surgery: A Systematic Review," in the Nov. 19, 2008, issue of JAMA, and in "Bariatric Surgery in Women of Reproductive Age: Special Concerns for Pregnancy." Printed copies of the report are available by calling 1-800-358-9295 or sending an e-mail to ahrqpubsahrq.hhs.

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