Some obese individuals turn to bariatric surgery to lose unnecessary weight but it appears that the surgery also has an effect on pregnant women. Findings of a new study suggest that women who have gone through weight loss surgery were less likely to suffer from diabetes during pregnancy.

For the new study published in the New England Journal of Medicine on Feb. 26, Kari Johansson, a nutritionist at the Karolinska Institute in in Stockholm, and colleagues compared the pregnancies of almost 600 women who gave birth after undergoing bariatric surgery and over 2,300 women with the same BMI but did not have the surgery using data from Swedish health registries.

Johansson and colleagues found that 2 percent of the women who had bariatric surgery developed gestational diabetes, which is significantly lower compared with the 7 percent in the other group of women. The women in the weight loss group were likewise found to have lesser odds of giving birth to babies, whose size are larger than normal.

The women in the weight loss group, however, were twice more likely to have babies that are small for their gestational age. The duration of their pregnancies was likewise shorter and they had higher incidence of stillbirths.

"Bariatric surgery was associated with reduced risks of gestational diabetes and excessive fetal growth, shorter gestation, an increased risk of small-for-gestational-age infants, and possibly increased mortality," the researchers wrote.

The researchers did not investigate what possibly caused the bariatric surgery patients to have smaller babies or higher incidence of stillbirth but said that it may possibly be due to the reduced nutrient absorption of the women as a result of the surgery causing the developing fetus in the womb to not receive enough nutrition.

The researchers said that some women may also continue trying to lose weight even when they are already expecting and this could have unwanted effects on fetal nutrition and growth.

"It has been reported that gastric bypass [a form of bariatric surgery] increases the risk of protein, iron, vitamin B12, vitamin D and calcium deficiencies," Johannson said.

Johansson said that because weight loss surgery preceding pregnancy has positive and negative effects, pregnant women who had bariatric surgery should be considered as risk pregnancies. They should be given special maternal health services care, detailed dietary guidelines which include monitoring their intake of post-surgery supplements, and extra ultrasound scans to track fetal growth.

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