Outcomes of in-vitro fertilization after bariatric surgery: a national register-based case–control study

STUDY QUESTION: Does previous bariatric surgery (BS) in women affect cumulative live birth rate in IVF? SUMMARY ANSWER: Women having had BS seem to have the same cumulative live birth rate as non-operated women of the same BMI at IVF treatment. WHAT IS KNOWN ALREADY: Because of the perinatal risks of obesity to mother and infant as well as impaired outcomes of IVF, obese women are advised to reduce their weight, but it is not clear whether previous BS could affect IVF results. STUDY DESIGN, SIZE, DURATION: This national register-based case–control study included all cases of BS (n = 30 436) undergoing IVF (n = 153) from 2007 until 2017. PARTICIPANTS/MATERIALS, SETTING, METHODS: Swedish women between 18 and 45 years operated with BS, with at least one first started cycle of IVF after surgery, were included. For each woman having IVF after BS (n = 153), up to five non-operated control women (n = 744) starting their first IVF cycle during the study period were matched for age, parity and BMI at treatment. The primary outcome in this study was the cumulative live birth rate (CLBR) after the first IVF cycle, defined as all live births after the first cycle including fresh and frozen embryo transfers. MAIN RESULTS AND THE ROLE OF CHANCE: There was no significant difference in CLBR between the BS group and the matched controls (29.4% compared to 33.1%), even though the number of retrieved oocytes (7.6 vs 8.9, P = 0.005) and frozen embryos (1.0 vs 1.5, P = 0.041) were significantly fewer in the BS group. There was no association between cumulative live birth and BS, adjusted odds ratio 1.04, 95% CI (0.73, 1.51). However, the birth weight was significantly lower in the children born to mothers with previous BS, mean (SD) 3190 (690) vs 3478 (729) g, P = 0.037. LIMITATIONS, REASONS FOR CAUTION: Confounders such as age, BMI and previous childbirth were accounted for by the matching design of the study, but there were no data on indication for IVF, anti-Müllerian hormone, smoking or previous comorbidities. The study was exploratory and did not reach sufficient power to detect potential smaller differences in live birth rates. WIDER IMPLICATIONS OF THE FINDINGS: The findings concur with those in previously published smaller studies and provide somewhat reassuring results considering IVF outcomes after BS with a CLBR comparable to that of controls, despite a lower mean birth weight. STUDY FUNDING/COMPETING INTEREST(S): This research was funded by grants from the Southern Health Care Region of Sweden. The authors have no competing interests to declare. TRIAL REGISTRATION NUMBER: N/A.