the risk of giving birth to a child with a birth defect does increase as the mother's age increases. this is probably due to abnormal division of the egg called nondisjunction. this leads to unequal chromosomes at the end of division. the traditional age at which a woman is considered to be at high risk for chromosomal abnormalities is 35. approximately 1 in 1 400 babies born from women in their 20s have down syndrome; it increases to about 1 in 100 babies born with down syndrome from women in their 40s.
does the risk of birth defects increase in a pregnancy after age 35?