I just wanted to add that I found a lot of inspiration from Dr. Randine Lewis as well. I'm not trying to sell anything here... but I came across her book in the library and ended up purchasing it. I highlighted all the areas that benefited me and to this day I use it as a reference book whenever I need inspiration. It is called The Way Of The Fertile Soul.
Just to give some perspective, the World Health Organization puts reproductive age at 15-49 years old. And even at 40 years old, the risk of Down's is still less than 1%.
I think in the West we're conditioned to assume that things go sharply downhill at 35, but I really think it depends from one person to the next! Factors like lifestyle, diet, and genetics all play big roles. Some women are in perimenopause by 35, others don't even get there til 55. And it's not set in stone, it can be influenced by our choices.
I found a lot of inspiration in Dr. Randine Lewis-- she specializes in fertility. If you're curious, she's worth googling. :)
Thats a tough question to answer. Even different Dr.'s will give differing opinions. Most seem to use 35 as the benchmark. You have an increased risk of miscarriage and an increased risk of chromosonal abnormalities, such as downs syndrome. Both of these issues are due to older eggs. After 35, in Canada anyway, amnio is automatically offered to test for chromosonal issues. That being said it is pretty common now for women to be having babies naturally and without issue well into their late 30's and early 40's. There are also many tests available as well as various treatments to assist her if she so chooses. I have talked to some Dr.'s that believe that "number" should be raised to 40.
All that being said, if a women want's to have children at any age (adult age of course), she should not be discouraged. Yes, it may be tougher to conceive and carry full term older, but many many women are doing it successfully. When to have children is a very personal decision and should never be dictated by anyone or anything other then her (and her partner's) own choice.