Fertility specialists have known for some time now that a woman’s chance to become pregnant and deliver a baby declines as she gets older. This is in part due to the fact that a woman is born with all of the eggs she is ever going to have in her life. All through her life, the number of eggs in a woman’s ovaries is decreasing. The eggs undergo a process of degeneration known as apoptosis. In fact, a much larger number of eggs are lost to degeneration than to ovulation. As a result, the age of menopause is unaffected by things that affect ovulation such as use of birth control pills, pregnancy or even the age that a woman starts having periods. It is greatly affected, however, by the number of eggs that a woman has at birth and the rate at which the eggs degenerate over time. Both of the factors have been suspected to have strong genetic influences.
In addition, eggs that “resisted” ovulation and thus sat in the ovaries for a long period of time, may be of poorer quality than those that were ovulated at a young age. The “older” eggs may be prone to damage in the DNA.
Recently, a study was presented at the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) and subsequently published in the journal Fertility and Sterility concerning over 200 women who conceived a pregnancy spontaneously after age 45. In characterizing these women, it was found that they have larger number pregnancies than expected on average and a lower miscarriage rate. Genetic profiling performed on eight of these women identified a clustering of genes that decreases apoptosis and increases DNA repair. The genes were not found in a control group of six women of the same age whose childbearing had ended at age 30. It is possible, that these older fertile women may have a unique genetic predisposition that protects them from the DNA damage and cellular aging that normally affects the ovary.
This finding, if confirmed in larger populations and other ethnic groups may serve to be able to predict women who are more likely to be able to conceive at an older age. Currently, an increasing number of older women are attempting pregnancy through in vitro fertilization and other technologies but with a very low success rate compared to younger women. The hope is that through profiling, to identify those women who are most likely to succeed and allow those women with a poor prognosis to avoid costly and ineffective treatments.