We read the study by Sheiner et al in the January issue of the American Journal of Obstetrics and Gynecology with great interest. We congratulate the authors with the important study that they have provided in the field of pregnancy after bariatric surgery. However, we do not agree with the author’s conclusion that the current recommendation to delay pregnancy after bariatric surgery can be discarded based solely on the results of their study.

Indeed, despite the efforts made by the authors to obtain comparable groups, the study is substantially biased by the overrepresentation of restrictive procedures in both groups (96.2% in the early group; 86.0% in the late group) and the much higher proportion of gastric bypass procedures in the late group (14.0% vs 3.8%). This difference is further accentuated because of the different group sizes (104 women in the early group vs 385 women in the late group). This means that only 4 patients with gastric bypass were included in the early group, compared with 54 patients in the late group. As the authors state, the difference between malabsorption-inducing (eg, Roux-en- Y gastric bypass) and restrictive procedures (eg, laparoscopic gastric banding, vertical-banded gastroplasty, and Silastic ring vertical gastroplasty) is substantial, not only in mechanism but also in clinical outcome and rate of complications. We fear that the far less aggressive restrictive procedures probably will have influenced the obstetric outcome positively in the early group.

When reviewing the relevant literature on the subject, we recently described severe fetal malformations caused by maternal vitamin deficiencies, especially in fat-soluble vitamins. These and other congenital malformations are an important concern and are more frequent after malabsorptive-type bariatric surgery. Despite the large total number of cases that were included, this study is underpowered to detect differences between both approaches in congenital malformations and other relatively rare events.

This retrospective study claims to have included all pregnancies after bariatric surgery, without any exception, between 1988 and 2008 that occurred in their center. It is unclear whether this includes all patients who underwent bariatric surgery in their center or all deliveries in the center that involved patients with a history of bariatric surgery. Besides the other limitations of a retrospective population-based study, this also could represent an important inclusion bias. Furthermore, the authors have reported previously on the outcome of pregnant patients after bariatric surgery from the same center. It is not detailed whether the current study represents a reanalysis on (partially) the same patients.

The current recommendations are based on the knowledge that severe weight loss during pregnancy results in adverse pregnancy outcome. Therefore, weight loss after bariatric surgery should be stabilized before pregnancy occurs, and this typically takes approximately 1 year.

As a result, we believe that pregnancies after bariatric surgery should be considered high-risk pregnancies and that the advice to delay pregnancy until after 12 months remains the safest approach in view of the current (limited) knowledge. We agree with the authors’ conclusion that a tailored approach for the individual patient after bariatric surgery is to be advised. In our opinion, this tailored approach should focus on providing effective contraception and nutritional advice during the period of rapid weight loss until a stable weight is obtained, rather than rushing the women into fertility programs.