Why do people say having children like after 35 is a bad thing?

Women can have babies until their bodies decide they can't. My mother had a daughter at 50 yrs old. My sister and sister in law both had babies at 49. It is harder to conceive as we age, and there is greater chance of abnormalities in the pregnancy and birth. The doctors watch you more carefully as you age. If you aren't ready, look into storing some of your eggs.