Woman's fertility starts declining in late twenties.

2002 MAY 30 - (NewsRx.com & NewsRx.net) -- A woman's fertility starts declining as early as her late 20s - not in her 30s as was previously thought, according to a study published in the European journal Human Reproduction.

The finding comes from a U.S.-Italian study of 782 healthy couples who were using natural family planning methods to avoid pregnancy.

Lead author Dr. David B. Dunson of the National Institute of Environmental Health Sciences said that, to his knowledge, this was the first study to observe that a woman's fertility started to decline before the age of 30.

However, he reassured women that this did not mean a lower overall probability of achieving pregnancy if they delayed trying to become pregnant until their late 20s or early 30s, but it did mean that it may take a month or two longer to become pregnant than it would have in their early 20s.

"Although we noted a decline in female fertility in the late 20s, what we found was a decrease in the probability of becoming pregnant per menstrual cycle, not in the probability of eventually achieving a pregnancy," he said.

The study found evidence that it is not only women who need to be concerned about their biological clock; men's fertility also begins to decline from as early as their late 30s.

However, there was some encouraging news for older would-be parents - age did not decrease the duration of the fertile window - the 6 days within the menstrual cycle when women were most likely to become pregnant.