Fathers Age Is Also a Factor in Fertility Does a fathers age affect fertility? (Francesco Tonelli for The New York Times) When it comes to age and fertility, women fear a biological clock and are urged to have children early. But men are rarely given the same advice and often dont worry about fertility when postponing marriage and children. But a growing body of research now shows the age of the potential father matters too. French researchers have collected data from more than 21,000 artificial inseminations involving 12,200 infertile couples. The data, presented yesterday at the 24th annual conference of the European Society of Human Reproduction and Embryology in Barcelona, found that pregnancy rates decrease and miscarriages increase when a father is over 35 years of age. Dr. Stephanie Belloc, of the Eylau Centre for Assisted Reproduction in Paris, said this is the first time that such a strong paternal effect on reproductive outcomes has been shown. In most of the cases studied, the couples were being treated because of the husbands infertility, but the researchers analyzed the results in a way to separate out the male and female factors related to each pregnancy. The sperm of each partner was examined for a number of characteristics, including sperm count, motility and morphology. Clinical pregnancy, miscarriage and delivery rates were also recorded. As expected, maternal age was a strong predictor of success. Intrauterine insemination, or IUI, led to pregnancy in 14.5 percent of women under 35, but just 8.9 percent in older women. Miscarriage rates were also typically affected by maternal age. But notably, a similar effect was shown for men over 35, in both pregnancy rates and miscarriage rates. This research has important implications for couples wanting to start a family, Dr. Belloc said. Our research proves for the first time that there is a strong paternal age-related effect on IUI outcomes, and this information should be considered by both doctors and patients in assisted reproduction programs. Because the data are based on men with known fertility problems, its not clear whether the results apply to all men as they age. However, previous studies have also suggested that the biological clock ticks for men too. To learn more, read this 2007 story from The Times.