Hi A. and Hannah,
Metformin is used to treat insulin resistance, which is a hallmark symptom of PCOS as well as of type II diabetes. This does not necessarily mean that you have either disease, however, so your doctor should establish just cause before just using a shot-gun approach.
PCOS (polycystic ovarian syndrome) is a disease in which a woman produces too much of the male sex hormones (androgens). BTW, all women make androgens naturally and they are important for muscle development, mental faculties, etc. as they are in men. As part of the disease, multiple cysts can form in one or both ovaries. Women with PCOS are often hirsuite (hairier than normal), overweight to obese, and typically have irregular menstrual cycles. For some of these symptoms, it is unclear whether they contribute to the cause or are an effect of PCOS.
The hormonal abberations associated with PCOS can make it difficult to conceive, but apparently another big factor is the insulin resistance associated with the disease (which can also be a contributing factor in the weight issues). When cells can't take in insulin (insulin resistance), they cannot regulate their uptake of glucose effectively. Glucose is the basic energy currency of cells, so without glucose, cells can't function well -- it would be like trying to run your car on an empty tank all of the time.
If you ARE insulin resistant, then taking metformin can correct that, making it possible for your ovaries to function properly and regulating your cycle. When your cycle is regular, it is easier to conceive. Metformin is an established and FDA approved treatment for infertility resulting from insulin resistance associated with PCOS. Incidentally, some research has shown that eating 1/4 to 1/2 teaspoon of cinnamon daily has the same effect as taking Metformin in diabetics. I don't know if anyone has investigated this effect in patients with PCOS. If you ARE NOT insulin resistant, then I doubt the Metformin will help at all.
Your doctor would have to do a series of tests to establish insulin resistance. You can look this up at labtestsonline.com.
Good luck to you!
R.