Clomid and fertility

I am 39 years old and was evaluated by infertility specialist. Everything was normal (HSG, FSH, ultra sound, prolactin , estrogen, TSH) and semen analysis in my husband.  No other medical problems or obesity.
We will try with clomid for two or three cycles.
What are the changes for conception?
What is the usual cause of infertility? Quality of eggs?
With IVF (if we decide to do it in the future), how can be decrease a chance for multiple births?
Thank you

[Shayne Plosker, MD]

Dear mary2-

Chances with clomid are not great, but as it is much cheaper and much less invasive than IVF, worth an initial try. Success with clomid and IUI for someone who is 39 is at best 5%-7% each month.

Regarding IVF, at age 39 the problem is that your chances of going home with a baby from an IVF cycle are only in the 20%-22% range, and the best way of maximizing these chances is by transferring back 3-4 embryos. Risk of triplets is very low, but risk of twins is probably in the 30% range if you get pregnant. The only way to lower this risk is to put back fewer embryos, but at age 39 doing so will dramatically decrease chances of success. Difficult decisions....

[lsim]

A related discussion, First IUI and 2WW!!  HELP!! was started.