Biological Clocks Ticking Fast

New research shows the decline in fertility as people age may be happening at faster rates than once believed.

Most studies on age-related changes in fertility have not separated changes due to a reduction in the frequency of sexual intercourse from changes directly related to aging. Researchers from the University of Padua in Italy studied more than 780 couples who were using natural methods to conceive. They compared the length of the fertile window between men and women of different age groups and they estimated the probability of conception occurring on a specific day.

Results show nearly all pregnancies occurred within a 6 day fertile window and there was no difference in the length of that fertile window in older men or women. However, researchers did find the probability for pregnancy was twice as high for women between 19 and 26 when compared to women ages 35 to 39. The previous belief was that fertility begins to drop significantly when a woman is in her early thirties. This new study shows that drop actually starts to happen at about age 27.

Women are not alone when it comes to age affecting their fertility. Previous studies show men’s fertility begins to decline in their forties or fifties. This study shows men’s fertility significantly drops after age 35. In fact, a 40-year-old man is 40 percent less likely to get his partner pregnant in a month than he was at age 35.

After further review, researchers found a 35-year-old woman who was with a man the same age had about a 29-percent chance of getting pregnant in one month. However, a 35-year-old woman with a 40-year-old partner had only an 18-percent chance of conceiving in a month. Researchers say the man’s age only seemed to affect fertility when the woman was over 35. Authors of the study conclude, “Women’s fertility begins to decline in the late 20s with substantial decreases by the late 30s. Fertility for men is less affected by age, but shows significant decline by the late 30s.”

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