Bariatric Surgery for Prepregnancy Weight Loss: A Safe Approach?

George W. Citroner


October 17, 2018

The Harms of Obesity Before and During Pregnancy

Obesity is harmful to everyone's health. But obesity during pregnancy places not only the mother at risk, but also the most vulnerable of all at risk—the fetus and newborn. Recent research finds that a common weight-loss surgery can significantly reduce the risk for birth complications.[1]

Only about 45% of US women are at a healthy weight before pregnancy, according to the Centers for Disease Control and Prevention.[2] Obesity in pregnancy is associated with multiple poor health outcomes for mother and child.[3]

According to Kecia Gaither, MD, obstetrician/gynecologist, maternal-fetal medicine specialist, and director of perinatal services at NYC Health + Hospitals/Lincoln in New York, "Obesity has become a global pandemic, and its frequency increases on an exponential basis yearly. Many comorbid conditions align themselves with obesity in women of childbearing age, including infertility, hypertension, and diabetes."

Obesity has been associated with several labor and delivery complications, including induction of labor, prolonged labor, cesarean delivery, and postpartum hemorrhage.[4,5] It's likely that obesity among pregnant women is a significant factor in the rising maternal mortality rates in the United States.[6]

Obese women have increased insulin resistance in early pregnancy that can result in a large-for-gestational-age fetus in later pregnancy. This not only increases the risk for cesarean delivery but also contributes to early placental and fetal dysfunction that increases the risk for birth complications and infant mortality.[7]

Weight-Loss Surgery Before Conception

New research from Karolinska Institutet in Sweden[1] finds that obese women who lose weight through bariatric surgery before conceiving can have safer deliveries.

Olof Stephansson, obstetrician and researcher at Karolinska Institutet's Department of Medicine in Solna, Sweden, and lead study author, described the study's rationale. "We knew from beforehand that bariatric surgery influences pregnancy and fetal growth. Women with previous bariatric surgery were less likely to have gestational diabetes, and their babies were less likely to be large for gestational age."

He added, "We wanted to know how a previous bariatric surgery influenced delivery outcomes. Our hypothesis was that these women would be less likely to have complicated deliveries, although [in a previous study[8]] we did find a small increased risk for preterm birth."

The study compared deliveries in 1956 women who had experienced considerable weight loss after bariatric surgery (98% had a gastric bypass) with those of 4476 women who had not undergone weight-loss surgery. The delivery outcomes of interest were cesarean delivery; instrumental delivery (forceps or vacuum extraction); induction of labor; post-term pregnancy (gestational age ≥ 42 completed weeks); epidural analgesia; and delivery complications, including labor dystocia, fetal distress, peripartum infection, obstetric anal sphincter injuries, and postpartum hemorrhage (defined as blood loss ≥ 1000 mL within 24 hours after delivery).

The median interval from surgery to conception was 1.4 years, and the median interval from surgery to delivery was about 2 years. The mean loss in body mass index after bariatric surgery was 13.5 kg/m2 (38 kg).

Maternal Delivery Outcomes

Stephansson and colleagues found that women with a history of bariatric surgery had lower risks for instrumental and emergency cesarean delivery. Compared with matched control women, those who had undergone bariatric surgery had substantially lower risks for post-term pregnancy, induction of labor, epidural analgesia, and delivery complications (labor dystocia, fetal distress, peripartum infection, obstetric anal sphincter injury, and postpartum hemorrhage). Thus, the weight loss resulting from bariatric surgery was associated with improved delivery outcomes. Previous research has shown that bariatric surgery is associated with a reduced risk for large-for-gestational-age infants[9]; however, the beneficial effects on delivery outcomes in this study were independent of fetal growth.

However, the investigators cautioned that although having bariatric surgery before becoming pregnant is associated with improved maternal delivery outcomes, other adverse pregnancy and infant outcomes must be considered when assessing the benefits and risks of giving birth after bariatric surgery.

Nutrient Deficiencies

Gaither explained that "the most common adverse effects of any bariatric procedure are nutrient deficiencies. Vitamins A, B, and D; iron; calcium; certain fats; and other fat-soluble vitamins are most commonly affected."

She also thinks that women in the study didn't wait long enough before conceiving. "Because most of the weight loss and malabsorption effects are seen within the first 18-24 months after the procedure, I counsel women to not get pregnant during this critical period." (Current guidelines advise women not to conceive during the first year after bariatric surgery.[10])

When asked whether bariatric surgery could potentially have any adverse effects on the health of the fetus, Stephansson replied, "We need to learn more about this. But so far, we have not found any adverse effects in the infant, besides that it's more likely to be born moderately preterm. We also need more information on growth and development in childhood."

Effects on Fetal Development

According to the American Society for Metabolic and Bariatric Surgery, these procedures cause weight loss by restricting the amount of food the stomach can hold, which can cause malabsorption of nutrients and even hormonal changes.

Gaither explained that in the early trimester of pregnancy, the placenta functions to provide the embryo with certain proteins and fats, which are later supplied by the mother. Because certain fats are necessary for normal brain development, a lack of them could "impede normal myelination and other neuronal processes necessary for normal cognitive development," said Gaither.

She added that "vitamin B1, or thiamine, deficiency may additionally be seen with bariatric surgery patients or even in patients with hyperemesis gravidarum. In both cases, the deficiency affects neurologic, cardiac, and circulatory functionality of the mother, and if severe enough may result in the death of both mother and baby."

More Research Is Needed

Gaither said that many factors need to be considered to ensure the health of both mother and child after bariatric surgery. "There are various types of bariatric surgery, each with its own specific side effects. For women who are infertile and desire pregnancy to occur as a result of the weight loss, it's certainly imperative to discuss the surgical option that would best reflect the desire for pregnancy and the optimization of a healthy pregnancy outcome for both mother and child."

She thinks it's critical for any woman who has had bariatric surgery, particularly upon conceiving, to "begin supplementation of vitamins, especially folic acid, which is important for normal fetal neurologic development."

Stephansson concludes that "[b]ariatric surgery-induced weight loss appears to be beneficial for childbirth and in my opinion is the best option to achieve lasting weight reduction over time. However, more research on the association with preterm birth and childhood development is warranted."


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