Every month, the typical 40-year-old woman has a 5% chance of conceiving. A variety of elements are at work here. The average age of menopause is 51 years old. Menopause is defined as a woman having been menstrually free for a full year (12 months). Therefore, the odds that a women will conceive during her 40th year are 5%. It's important to remember that pregnancy rates decline after 40 because there are fewer eggs left to fertilize. Also, older mothers tend to have babies with health issues; about one in four children born to mothers over 35 is born premature, for example. Mothers over 40 have about a 1 in 8 chance of losing their baby during pregnancy or delivery. About 80% of women between the ages of 15 and 44 years old have produced a child through natural means. So although birthrates are down, reproductive capacity is not lost yet for the most part.