Effect of Age on Male Fertility

Studies from the Office of Health Research, Statistics and Technology of the U.S. Department of Health have made it clear that fewer than 1% of teenage girls are infertile, but more than 20% of women in their mid-30s are infertile. This decrease in fertility with age is not a new phenomenon that suddenly developed in the 1980s. Many studies in the past have consistently demonstrated a decrease in fertility of older couples. The question that this age-related decline in a couple's fertility brings up is to what extent it is the consequence of reduced female fertility, male fertility, or both. The first well controlled study on this issue came from France in 1982. It compared the results of artificial insemination with highly fertile donor sperm in 2193 nulliparous women who had azoospermic husbands. In order to control for the possibility that the age of the male partner might affect the infertility of an older couple, this huge series employed artificial insemination with uniformly fertile donor sperm to women of various ages over a prolonged period of time. The cumulative success rate (as well as the pregnancy per cycle) for women 25 years of age or younger was similar to that of women over 25 but under 31 years of age. However, there was a significant decrease in the pregnancy rate for women 31 to 35 years of age, and a dramatic decrease for women over the age of 35 years. Thus, the pregnancy rate per cycle and the overall cumulative pregnancy rate clearly went down with age in women in whom the male factor was constant, (i.e., only fertile donor sperm were used). This large French study proved the dramatic reduction in fertility of women as they pass the age of 30 years, becoming progressively more severe during their next 10 years. They separated the influence of the age of the woman from other variables associated with age, such as decreased frequency of sex with age as well as increased age of the husband. Their study completely ruled out those issues by using artificial insemination with frozen donor semen. A second problem they dealt with is that in many cases where the husband is "infertile" his sperm count is simply low, but he is definitely not "sterile. " An extremely fecund woman may thereby become pregnant easily by a man who is extremely infertile. Thus, in any group of women seeking artificial donor insemination whose husbands were merely oligospermic, there will be a significant number of such women who are more infertile than in a random population of women, and this may not be related to age. By choosing only women whose husbands were azoospermic, the French authors completely removed that bias. Thus, it was clear that female fertility declines dramatically with age and it becomes most pronounced and observable past the age of 35 years. Further evidence to this point comes from the extremely low pregnancy rates in women 40 years of age or older undergoing in vitro fertilization. The next most serious question (which has now been settled) related to decrease in female fertility with age is whether the problem is caused by the age of the ovaries (and in that respect the age of the oocyte) or if it is related in some way to the actual age of the woman. In vitro fertilization (IVF) and gamete intrafallopian transfer (GIFT) studies using eggs donated from younger women to postmenopausal women (often as much as 20 years older) have clari-