The success of these older-than-traditional women at childbearing belies the difficulty that many women over the age of thirty have in getting pregnant.
Successful conception depends on a variety of factors. A man has to produce an adequate amount of healthy sperm, and a woman has to produce healthy eggs. The sperm has to be able to travel up the fallopian tubes to reach the egg, and once there, it must be able to fertilize the egg. Finally, the fertilized egg must become a viable embryo and implant in the uterus.
Problems can occur in any one of these steps along the way and cause infertility. A man might not produce enough sperm, or his sperm might be unable to reach the eggs. A woman might have problems producing eggs or her fallopian tubes may be blocked.
Infertility becomes more pronounced for mature women who are attempting pregnancy because a woman's egg production decreases with age, especially after the age of 35.
Often, women will undergo treatments for infertility that range from taking hormones to stimulate ovulation to having their eggs harvested by doctors, fertilized by their partner's sperm outside their bodies, and finally having the early embryos implanted directly into their wombs (the technique of in vitro fertilization).
Despite the existence of these therapies, however, the molecular mechanisms that govern female infertility are not completely understood. In fact, the cause of infertility is not always easy to diagnose. The American Society for Reproductive Medicine estimates that the cause of infertility remains a mystery in about 20 percent of all cases.
One issue may be that once a woman's egg is fertilized and made into
Source:Scripps Research Institute