Obesity (defined as a BMI of 30 or more), especially extreme obesity, is known to decrease the likelihood that a woman can become pregnant. In addition, when obese women do become pregnant, they are more likely to develop gestational diabetes, and have an increased risk of large babies, early delivery, and stillbirths, and their infants are at increased risk of congenital malformations.
Losing weight prior to becoming pregnant decreases the risk of at least some of these negative outcomes. Bariatric surgery is an effective means of weight reduction, and is known to decrease the occurrence of type 2 diabetes. Whether or not weight loss via bariatric surgery will ameliorate the negative outcomes seen in pregnant obese women and their babies has not been firmly established.
Dr. Kari Johansson from the Karolinska Institute in Stockholm, Sweden and colleagues performed a retrospective analysis of Swedish birth records from 2006 through 2011. They identified 535 women who had become pregnant and given birth to single babies after undergoing bariatric surgery. Nearly all had the gastric bypass type of surgery. Each woman was matched with 5 control obese women who had not had gastric bypass surgery before pregnancy with respect to pre-surgery BMI, maternal age, smoking history, educational level and delivery year.
The average pre-surgery BMI was nearly 44, while that of the control women in early pregnancy was 42. On average, about one year elapsed between bariatric surgery and pregnancy, during which time the women lost an average of 37 kg (81 pounds).
In their analysis, the researchers found that the women who underwent bariatric surgery were significantly less likely to both: A-- develop gestational diabetes, and B--to have larger babies comma, than were the unoperated obese controls. Indeed, they were significantly more likely to have small-for-gestational-age infants. Further results showed a (not-quite-significantly) elevated risk of stillbirth and neonatal death; no differences in the frequency of infant malformations were seen.
In their discussion, the authors noted that this observational study could not determine a causal relationship between bariatric surgery and pregnancy outcomes. They also pointed out that Despite known adverse effects of gastric bypass surgery on the metabolism of iron, vitamin B12, and folate, we found no significant effect of bariatric surgery on the overall risk of congenital malformations.
ACSH s Dr. Ruth Kava commented Although, as the authors said, one can t assign causality in an observational study, it is reassuring to note that the women who had lost weight via bariatric surgery did not seem to suffer undue negative effects during pregnancy and nor did their infants