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.

到了一定年龄，当生育被提上日程时，女性会惧怕“生理钟”并急着尽早产子。但男性却罕被提醒，丝毫不担心推迟结婚和生子后的生育力问题。

但越来越多的研究表明这些未来爸爸的年龄同样会影响生育力。法国研究人员从12000例不育夫妇的超过21000例人工受精中收集数据。昨天，这些数据在巴塞罗那召开的第24届欧洲人类生殖及胚胎科学会议上被公布。从中显示当父亲超过35岁后，胎儿受孕率降低同时流产率升高。

巴黎艾劳辅助生殖中心（Eylau Center for Assisted Reproduction）的斯坦福尼.贝洛克博士表示父方在生殖中这么重要的影响还是首次发现。研究人员通过分离与每一例受孕情况相关的男性和女性因素，从而得出结论，在大多数被研究的对象中，是由于男方的不育而接受人工授精。每个研究对象的精子都经过了多项检测，包括精子数，精子活动力和精子形态。临床受孕率，流产率和分娩率也被记录。

与预期一样，母亲的年龄是生育成功与否的重要因素。子宫内受精，或人工授精(IUI)能使14.5%的35岁以下女性受孕，而在35岁以上女性中，却只有8.9%。而流产率很大程度上也受父方年龄的影响。

“这项研究对正准备组成家庭的夫妻有着重要的意义。”贝洛克博士说，“我们的研究首次证实了在人工授精的结果上强烈的父方因素的影响，而这些信息将会被辅助生殖项目的医生和病患所考虑。”

因为这些数据是以有已知生育问题的男性为基础而得出的，所以还不清楚它是否适用于同年龄的所有男性。而先前的研究显示男性同样也有生理钟。要了解更多，请阅读纽约时报2007年的相关报道。