One of the main reasons women with PCOS are encouraged to take metformin is because it is widely believed that it can help to improve fertility and reduce the incidence of miscarriage.
A 2009 study challenges this belief. It comes from the Cochrane Collaboration, a not-for-profit organization that evaluates groupings of research independent of for-profit (read"drug company") funding. I like their studies because their sample sizes are large and their findings are evidence-based. It takes them a long time to adopt new ideas, but it is because they so heavily scrutinize the available information rather than jumping on any bandwagons.
In this study, authors searched several comprehensive medical databases for studies evaluating metformin used during in-vitro fertilization (IVF) or intra-cytoplasmic sperm injection (ICSI). They specifically looked at randomized, controlled trials containing a"no treatment" or placebo group to compare to a group receiving metformin. They evaluated several types of outcomes that metformin may have an opportunity to influence: live birth rate, pregnancy rate, miscarriage rate, incidence of ovarian hyperstimulation syndrome, patient-reported side effects, and several hormone levels (estradiol, androgen, fasting insulin and glucose).
This exhaustive review, under rigorous statistical analysis…
"found no evidence that metformin treatment before or during assisted reproductive technique (ART) cycles improved live birth or clinical pregnancy rates."
The one benefit of metformin appeared to be a reduced risk of OHSS in women with PCOS and undergoing IVF or ICSI cycles.
I'm not a physician and therefore, I am not able to prescribe metformin. And I am ABSOLUTELY NOT ENCOURAGING ANYONE READING THIS TO DISCONTINUE USING MEDICATION THAT THEY HAVE BEEN PRESCRIBED. I do, however, see a tendency to hand this medication out without evaluating whether or not it is appropriate. It's important to discuss such issues with your physician and to be sure they are aware of the research supporting (or not supporting) their recommendation.
Here is the reference for anyone who wishes to share it with their personal provider.
Tso LO, Costello MF, Albuquerque LE, Andriolo RB, Freitas V. Metformin treatment before and during IVF or ICSI in women with polycystic ovary syndrome. Cochrane Database Syst Rev. 2009 Apr 15;(2):CD006105.