Research: Male Biological Clock Winds Down After 35


Paternal age and obesity diminish fertility

SAN RAMON, CALIFORNIA – Infertility physicians at Reproductive Science Center of the Bay Area have found that their male patients follow the findings of a recent study that indicated sperm quality begins to deteriorate after age 35.

According to the new study reported in the Aug. 1 issue of Obstetrics and Gynecology, sperm quality starts to go downhill after age 35 and indicates that paternal age is a significant risk factor for miscarriage. The study of almost 14,000 pregnancies, conducted by Dr. Karine Kleinhaus of Columbia University, showed that women with partners ages 35 or older had nearly a threefold increase in spontaneous abortions compared with women whose partners were younger than 25.

“Many of the male patients we treat were married later in life or in the course of their second or third marriages found they were unable to conceive–even if they had children from a previous marriage,” says Dr. Kirsten Ivani, IVF lab director of the Reproductive Science Center of the San Francisco Bay Area (RSC). “Sperm quality is clearly impacted as child-bearing is increasingly delayed – for both men and women. It is already well documented that fertility declines because of a limited number and quality of eggs for women as they get older, so this is research should alert men to similar issues.”

It may be that the clock ticks even faster for overweight men. New research from the National Institute of Environmental Health Sciences showed that men with increased body mass index (BMI) were significantly more likely to be infertile than normal-weight men. A 20-pound increase in men’s weight may increase the chance of infertility by about 10 percent. The majority of men who participated in the study were more than 30 years old. Obesity affects nearly one-third of the adult American population (approximately 60 million).

According to the American Obesity Association, the number of overweight and obese Americans has continued to increase since 1960, a trend that is not slowing down. The Columbia research found that the risk of miscarriage of a fetus conceived by a father over age 40 was 60 percent greater than if the father were 25 to 29, irrespective of other factors that have been linked with increased miscarriage risk, such as the mother’s age, maternal diabetes, poor maternal health and smoking during pregnancy. The increased risk of miscarriage does not just apply to fathers in their 40s, however. The miscarriage risk in a pregnancy involving a father aged 35 to 39 was three times higher than the risk if the father were under 25.

Data from the study showed that 1,500 of the women suffered miscarriages, while 12,000 carried their children to term. “This new study provides important information for people – of all ages – who are planning their families,” says Dr. Ivani. “It means that men should be sure to get the medical attention they need to uncover medical problems underlying infertility.”

In fact, the American Society for Reproductive Medicine (ASRM) has set an upper age limit of 40 years old for semen donors because of the increased risk of genetic abnormalities in the offspring of older fathers. According to the ASRM, infertility is a male problem 35 percent of the time; a female problem 35 percent of the time, a combined problem of the couple 20 percent of the time, and the final 10 percent is unexplained.


Reproductive Science Center

Established in 1983, two years after the first successful birth through in vitro fertilization (IVF) in the U.S., Reproductive Science Center of the San Francisco Bay Area was responsible for the nation’s second successful birth of a baby from a frozen embryo. Today RSC is recognized for its pregnancy rates and work with egg donors and egg recipients from Northern California, the U.S., Asia, India and from around the world. RSC is a trusted destination for patients pursuing medical tourism. For more information, please visit

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