Advanced female reproductive age is an important factor when evaluating couples for infertility. Infertility is defined as a lack of pregnancy after 12 months of unprotected intercourse, a condition present in about 15% of couples of reproductive age. The proportion of couples considered infertile has not changed recently in spite of an increase in the number of couples seeking infertility evaluation and treatment. Reasons for this phenomenon include the aging of the baby-boom generation, deferment of childbearing to later years of reproductive life (because of changes in lifestyles), and increased exposure of patients to infertility services. More women are delaying childbearing until their late 30's and into their 40's for various reasons, one of them being to develop their professional careers. This voluntary delay in childbearing not only poses a problem in terms of the 30–50% reduced pregnancy potential of older women, but other risks also have to be taken into account: the effect of pregnancy on other maternal illnesses, an increased risk of pre-eclampsia, hypertension and diabetes, and an increased risk of chromosomal abnormalities, abortions, and stillbirth. The decrease of female fecundity beginning in the 30's, becoming more pronounced after 40, is well documented. There is an approximately 50% decrease in the fertility rate of women attempting pregnancy at the age of 40 or older compared with younger women, and a twofold to threefold increase in the rate of spontaneous abortions. Reports of artificial insemination and chromosomal analysis of unfertilized human oocytes and spare embryos in in vitro fertilization (IVF) suggest that the quality of the oocyte and the resulting embryo are affected seriously by age; again, an age of 40 years being the critical cutoff point. On the other hand, age (up to 64 years) does not seem to affect sperm characteristics or its ability to fertilize human eggs, and the resulting embryo development in vitro as well as implantation in recipient uteri are not affected by the age of the male providing the semen sample.