top of page

BAMBINI trial: Bariatric surgery superior to medical care for treating PCOS

Bariatric surgery is superior to medical care for treating women with polycystic ovary syndrome (PCOS), oligomenorrhoea or amenorrhoea and obesity, according to the findings from the Bariatric Surgery vs Medical Care For Obesity And Polycystic Ovarian Syndrome Related Infertility (BAMBINI) randomised controlled trial, published in the Lancet. Patients who underwent surgery also experienced a greater increase in spontaneous ovulation rate, cardiometabolic risk factors, psychological health and quality of life at 52 weeks of follow-up, compared with those who received medical care.

Alexander Miras

“To our knowledge, BAMBINI is the first RCT to compare the effect of bariatric surgery with medical care in women living with PCOS, obesity, and oligomenorrhoea or amenorrhoea. The trial showed that women after vertical sleeve gastrectomy had a significantly higher rate of spontaneous ovulatory events, approximately 2.5 times greater than that of the medical group over the 52-week follow-up period,” explained Dr Alexander D Miras from Imperial College London, London and Ulster University, Derry, UK, co-author of the paper. “Ovulation was confirmed biochemically using weekly serum progesterone measurements. Participants in the surgical group had significantly greater improvements in anthropometrics, cardiometabolic risk factors, biochemical hyperandrogenism, quality of life, and psychological health compared with the medical group. There were no significant differences between the groups in clinical hyperandrogenism.”

PCOS is the most common cause of anovulatory infertility and obesity is known to  exacerbates the reproductive complications of PCOS. However, bariatric prior to BAMBINI, the efficacy of surgery on ovulation rates has not yet been compared with behavioural modifications and medical therapy in a randomised trial. Therefore, researchers from the UK designed a RCT to compare the safety and efficacy of bariatric surgery versus medical care on ovulation rates in women with PCOS, obesity and oligomenorrhoea or amenorrhoea.

The study recruited 80 women with a diagnosis of PCOS (based on the 2018 international evidence-based guidelines for assessing and managing PCOS) and a BMI of 35 kg/m2 or higher. Participants were randomly on a 1:1 ratio to the medical or surgical group and underwent assessments by a physician, dietitian, psychologist, and surgeon.

Lifestyle modification was performed by specialist dietitians at online group sessions and one-to-one consultations every two weeks for the first 26 weeks of the trial and subsequently once every four weeks for the remaining 26 weeks.  In the surgical group, participants were postoperatively assessed by a clinical nurse specialist at ten days, six months and 12 months, and by a dietitian at three months. The primary endpoint was the number of biochemically confirmed spontaneous ovulatory events (measured by weekly serum progesterone) expressed as an incidence ratio over 52 weeks.

A total of four participants in the surgical group did not receive the intervention and three participants in the medical group were lost to follow-up, and two dropped out due to work commitments. In the surgical group, five participants were lost to follow-up. Therefore, 63 (79%) of the participants completed the trial.


In the intention-to-treat analysis, the incidence rate for the primary endpoint was 4.1 events per year in the surgical group and 1.9 events per year in the medical care group (p<0.0007). Similar results were obtained from the per-protocol analysis (p<0·0010). The difference in the incidence of ovulatory events between the groups was evident by 8 weeks after the intervention and increased further over 52 weeks.

Participants in the surgical group experienced a significant reduction in weight (125.2kg at baseline and 89.5 kg at 52 weeks), but not the medical group (116.3kg at baseline and 118.7kg at 52 weeks). Moreover, there was a significant reduction in waist circumference and a decrease in glycated haemoglobin in the surgical group, as well as significant differences in systolic blood pressure, diastolic blood pressure, fasting glucose, fasting insulin, and triglyceride concentrations between the medical and surgical groups at 52 weeks. There was a significant reduction in HOMA-IR in the surgical group, but not in the medical group, with a significant difference between the groups at 52 weeks.

“Due to the absence of RCT evidence, the diagnosis of PCOS and obesity has yet to feature explicitly in national or international guidelines as an indication for bariatric surgery.49 The results of this trial could inform guidelines and medical insurance providers to offer bariatric surgery to increase the prospects of fertility for women with obesity, PCOS, and oligomenorrhoea or amenorrhoea,” the authors concluded. “In fact, the second International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome now recommends bariatric surgery as a treatment option to improve cardiometabolic risk factors, ovulation, and pregnancy rates in women with PCOS and obesity.”

The findings were featured in the paper, ‘Bariatric surgery for spontaneous ovulation in women living with polycystic ovary syndrome: the BAMBINI multicentre, open-label, randomised controlled trial’, published in The Lancet. To access this paper, please click here


bottom of page