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 don't 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 husband's 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, it's 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.

到了一定年齡，當生育被提上日程時，女性會懼怕“生理鐘”并急著盡早產子。但男性卻罕被提醒，絲毫不擔心推遲結婚和生子后的生育力問題。

但越來越多的研究表明這些未來爸爸的年齡同樣會影響生育力。法國研究人員從12000例不育夫婦的超過21000例人工受精中收集數據。昨天，這些數據在巴塞羅那召開的第24屆歐洲人類生殖及胚胎科學會議上被公布。從中顯示當父親超過35歲后，胎兒受孕率降低同時流產率升高。

巴黎艾勞輔助生殖中心（Eylau Center for Assisted Reproduction）的斯坦福尼.貝洛克博士表示父方在生殖中這么重要的影響還是首次發現。研究人員通過分離與每一例受孕情況相關的男性和女性因素，從而得出結論，在大多數被研究的對象中，是由于男方的不育而接受人工授精。每個研究對象的精子都經過了多項檢測，包括精子數，精子活動力和精子形態。臨床受孕率，流產率和分娩率也被記錄。

與預期一樣，母親的年齡是生育成功與否的重要因素。子宮內受精，或人工授精(IUI)能使14.5%的35歲以下女性受孕，而在35歲以上女性中，卻只有8.9%。而流產率很大程度上也受父方年齡的影響。

“這項研究對正準備組成家庭的夫妻有著重要的意義。”貝洛克博士說，“我們的研究首次證實了在人工授精的結果上強烈的父方因素的影響，而這些信息將會被輔助生殖項目的醫生和病患所考慮。”

因為這些數據是以有已知生育問題的男性為基礎而得出的，所以還不清楚它是否適用于同年齡的所有男性。而先前的研究顯示男性同樣也有生理鐘。要了解更多，請閱讀紐約時報2007年的相關報道。