Bariatric Surgery Before Pregnancy Lowers Risk for Gestational Diabetes

Bariatric surgery was linked to positive outcomes in pregnancy, such a reduced risk for gestational diabetes and excessive fetal growth, according to data from a population-based study.  However, this study was also associated with negative outcomes, including an increased risk for small-for-gestational age infants and possibly increased mortality. These findings suggest the need for increased monitoring during pregnancy, the study authors reported in the February 26 issue of the New England Journal of Medicine.

“Since bariatric surgery followed by pregnancy has both positive and negative effects, these women, when expecting, should be regarded as having high-risk pregnancies,” said Kari Johansson, PhD, a nutritionist in the Department of Medicine, Solna, Karolinska Institutet, Stockholm, Sweden. “They ought to be given special care from the maternal health services, such as extra ultrasound scans to monitor fetal growth, and detailed nutrition advice that includes checking the intake of the necessary post-surgery supplements.”

The Risks of Obesity During Pregnancy
Women with obesity are at increased risk for development of gestational diabetes, delivery complications, obesity in offspring, stillbirth, and preterm birth among other complications. Previous studies on the effects of pre-pregnancy bariatric surgery have shown inconclusive results or were limited by small sample sizes, heterogeneous study design, and lack of matching for pre-surgery body mass index (BMI).

“The effects of bariatric surgery on health outcomes such as diabetes and cardiovascular disease have been studied, but less is known about the effects on pregnancy and perinatal outcomes,” said Dr. Johansson. “Therefore, we wanted to investigate if the surgery influenced in any way the risk of gestational diabetes, preterm birth, stillbirth, if the baby was small or large for its gestational age, congenital malformations, and neonatal death.”

Johansson et al used 2006 to 2011 data from the Swedish Medical Birth Register. Of 628,778 singleton pregnancies, 596 were in women who underwent bariatric surgery before 2011 for whom data on pre-surgery BMI was available. Each of these pregnancies was compared up to 5 control pregnancies in women with obesity who did not receive bariatric surgery and were matched for pre-surgery BMI, age, parity, smoking history, educational level, and delivery year.

Lower Risk for Gestational Diabetes Found in Women Who Underwent Bariatric Surgery
Women who underwent bariatric surgery had a significantly lower risk of gestational diabetes and large-for-gestational-age infants (Table). In contrast, women in the bariatric surgery group were more than twice as likely to give birth to babies who were small-for-gestational-age. While the risk of preterm birth was similar among the 2 groups, women in the bariatric group were significantly more likely to have pregnancies of a shorter duration (273.0 vs 277.5 days; P<0.001).

Table. Maternal and Infant Outcomes Among Women With or Without Bariatric Surgery Matched for Pre-surgery BMI

a>90th percentile; bbirth weight >4,500 g; c <10th percentile
Data extracted from Johansson et al. N Engl J Med. 2015;372(9):814-824.


The risk for stillbirth or neonatal death was slightly higher in the bariatric surgery group than the control group; however, this difference was not statistically significant (1.7% vs. 0.7%, respectively; P=0.06). No difference in the rate of congenital malformations was found between the two groups.

Similar Findings Reported in a Meta-analysis
Similar findings were reported in a meta-analysis on this topic in the March issue of the International Journal of Gynaecology and Obstetrics. The findings showed that women with obesity who had undergone bariatric surgery had a lower risk for gestational diabetes, hypertensive disorders, and macrosomia, but a higher risk for small-for-gestational-age newborns compared to women with obesity who did not have bariatric surgery.

“The large number of samples [in the Johansson study] made its conclusions more reliable and objective,” said Zhi-hong Wang, MD, PhD, Chief Physician and Associate Professor in the Department of Endocrinology at First Affiliated Hospital of Chongqing Medical University, Chongqing, China. “Before the study by Johanssen et al, little research could make such a forceful conclusion," she said.

Dr. Wang added that women who are contemplating bariatric surgery before pregnancy should be given a full understanding of the pros and cons of each type of bariatric surgery. In addition, she recommended “close follow-up of fetal weight in order to prevent the occurrence of low birth weight in the fetus and long-term follow up with a nutritionist for the mother.”

“We think bariatric surgery is beneficial to women with morbid obesity,” Dr. Wang said. “Morbid obesity can cause menstrual disorders and ovulation inhibition, and finally lead to infertility. Even if these women become pregnant, they may still suffer from metabolic disturbances [that] influence fetal growth. What’s more, they have a higher incidence of infection and hemorrhage during delivery,” Dr. Wang said.

Continue Reading:
Bariatric Endocrinology: 2015 Update
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