Outcomes of Pregnancy After Bariatric Surgery

Published - Written by Daniela Lamas

Your patient has been trying to lose weight for years.

But no matter how many grapefruits she eats, whether she goes ‘gluten free’ or replaces her snacks with lean meats and long walks on the treadmill, the 35-year old’s weight has hit a plateau. And with the weight have come a series of troubling health effects, most recently high blood pressure and sleep apnea.

It’s time to consider bariatric surgery. She’s nervous but excited. You’ve referred a few patients to bariatric surgery before, so you’re prepared for most of her questions. But then she comes up with a question that has you stuck.

Your patient hopes to get pregnant in the future. Will her pregnancy face the same potential for poor outcomes – gestational diabetes, large birth and congenital malformations among them – as it would if she conceived now, prior to bariatric surgery? On the other hand, she wonders, does bariatric surgery bring with it a new host of pregnancy-related risk?

You aren’t sure. You know well that maternal obesity would place your patient and fetus at risk for gestational diabetes, complications with delivery, some congenital malformations and preterm birth. You know, too, that bariatric surgery can normalize glucose control in diabetics. But without a large-scale study investigating the effect of bariatric surgery on gestational diabetes on pregnancy outcomes, you aren’t sure how to respond.

A study published in this week’s NEJM might help answer your patient’s question.

In their paper, “Outcomes of Pregnancy in Women with Prior Bariatric Surgery,” Kari Johansson and colleagues set out to assess the risk of gestational diabetes, large-for-gestational-age (LGA) birth, small-for-gestational-age (SGA) birth, stillbirth, neonatal death and major congenital malformations in infants born to women who had undergone bariatric surgery.

To conduct this population wide study, the investigators tapped into the Swedish health system’s extensive nationwide registers and came up with 670 births to women who had undergone bariatric surgery and had a pre-surgery BMI recorded. The vast majority of these bariatric procedures were gastric bypass. The researchers then compared outcomes to another group of women who hadn’t undergone surgery and whose pre-pregnancy BMI was similar to the the pre-surgery BMI of the bariatric surgery group.

Their results? As expected, patients who had undergone bariatric surgery had lower rates of gestational diabetes (in just below two percent of the post-surgery group compare to nearly seven percent of the control group). As for the babies, post-surgery births were less likely to be large-for-maternal age – but more likely to be small-for-maternal age. While post-surgery pregnancies were shorter on average, there was no significant risk in the difference of preterm birth and no difference in the frequency of congenital malformations.

On a more troubling note, there was a suggestion of a higher risk of stillbirth and neonatal death in the infants delivered to post-surgery mothers (1.7 percent versus 0.7 percent), but this did not meet the cut-off for statistical significance.

The authors acknowledge some limitations to their study. It is an observational study and thus can’t make a determination as to cause and effect. Furthermore, as the Swedish population is mostly Caucasian, findings are not necessarily generalizable to other groups.

In an accompanying editorial, Aaron B. Caughey, who chairs the department of Obstetrics and Gynecology at Oregon Health and Science University, notes that with expanding rates of obesity in the US, obstetricians can expect to see an increasing number of women who have undergone bariatric surgery. While the current study does not lead to any direct change in management, he notes, “decisions regarding bariatric surgery in women of reproductive age should take into account the benefits and risks associated with this not inconsequential procedure in terms of both pregnancy and long-term health.”