Bariatric Surgery Linked to Increased Risk of Premature Birth and Low Birth Weight

Premature Baby in IncubatorWomen who have undergone bariatric surgery to lose weight are at an increased risk of giving birth prematurely and giving birth to babies with low birth weight compared to women who have not had weight loss surgery, says a new study published in the journal BMJ.

Researchers at the Karolinska Institutet in Sweden recently compared the perinatal outcomes in births of women with a history of bariatric surgery versus women who had never undergone the weight loss procedure.

Using a population-based matched cohort study within the Swedish national health service, the researchers looked at 1,742,702 singleton births from 1992 through 2009. The researchers then matched up to five control births by maternal age with each mother who had undergone bariatric surgery prior to pregnancy. Maternal BMI, educational background, smoking habits, and previous births were almost matched between the study group and control group.

After matching the mothers who had undergone bariatric surgery with the control group, the researchers examined preterm birth (born at less than 37 weeks), small for gestational age birth, large for gestational age birth, stillbirth (death before birth after 28 weeks), and neonatal death (death between birth and 27 days).

Of the babies who were considered small for gestational age, 5.2% were born to mothers who had undergone bariatric surgery versus 3% who were born to mothers who had not had the weight loss surgery. Only 4.2% of babies born to mothers who had had the surgery were considered large for gestation compared with 7.3% within the control group.

Mothers who had undergone bariatric surgery were also at an increased risk for premature birth, with 9.7% of the study group born premature versus 6.1% in the control group.

The researchers found no difference between the study and control groups in terms of stillbirth and neonatal death.

Dr. Olof Stephansson at the Clinical Epidemiology Unit at Karolinska Institutet explains the findings:

“Mothers with the same BMI gave birth to babies of varying weights depending on whether or not they had undergone bariatric surgery, so there is some kind of association between the two.

“The mechanism behind how surgery influences fetal growth we don’t yet know, but we do know that people who have bariatric surgery are at increased risk of micronutrient deficiencies.”

The researchers recommend that doctors inform women who are considering bariatric surgery about the increased risk of premature birth and low birth weight. Pregnant women who have undergone weight loss surgery should also be considered high risk and should receive more attentive prenatal care.


Bariatric surgery in women linked to premature birth:
Perinatal outcomes after bariatric surgery: Nationwide population based matched cohort study:

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