Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) appear to result in similar rates of fetal growth restriction, according to French researchers

"Our study is the first clearly showing that SG induces the same fetal growth restriction as RYGB," the team note in Surgery for Obesity and Related Diseases, online July 20.

In their study, they found fetal growth after bariatric surgery was positively tied to protein supply but inversely tied to maternal iron status. In addition, the mean number of maternal nutritional deficiencies was similar in the two groups.

"Protein intake has to be carefully assessed during pregnancy after bariatric surgery, and we recommend referring pregnant women systematically to a dietitian because they often have difficulties eating meat," co-authors Dr. Muriel Coupaye and Dr. Severine Ledoux of Paris Diderot University told Reuters Health in a joint email. "A careful nutritional survey is required during pregnancy, whatever the bariatric procedure."

Bariatric surgery

Most research has shown improved pregnancy outcomes after bariatric surgery, but an increased risk of newborns who are small for gestational age has been reported following RYGB. It's theorized that this growth restriction is caused by maternal nutritional deficiencies, which in turn can arise following at least some types of bariatric surgery.

The French researchers examined records of women from a prospective single-center database, started in 2004, of severely obese women who underwent bariatric surgery. Study subjects were all women with a singleton pregnancy after undergoing RYGB or SG and who had had at least one nutritional assessment at the host institution.

The 111 women included in the analysis had 123 singleton pregnancies (77 after RYGB and 46 after SG) between 2006 and 2017. Mean pre-pregnancy body mass indexes were similar between the two groups.

In the 110 pregnancies for which outcomes were known, there were no significant differences between the two groups in rates of hypertension, pre-eclampsia, gestational diabetes, C-section, gestational age at delivery, preterm delivery, birth weight, birth weight Z-score, small for gestational age or Apgar score.

According to second-trimester nutritional assessments, protein intake was significantly lower in women who had undergone SG. Using pregnancy norms, selenium and iron deficiencies were the most prevalent nutritional deficiencies in both groups.

The researchers note that the women in the study took fewer iron supplements than recommended during pregnancy after bariatric surgery, but that iron intake was not associated with fetal growth. The underlying mechanisms, the researchers add, remain to be clarified.