NOW THAT MOST women are glumly grappling with the widespread medical consensus that, if you want to have a baby, you'd best do it by age 35, here comes more exciting news from the research community: Firstborn children to mothers under 25 are nearly twice as likely to live to be 100 than those born to mothers over 25. In terms of public relations, the ad lines write themselves: Give your baby the gift of a century, have him when you're barely done with college. As a bonus, teenage moms might finally catch a break.

"What is really interesting is that the survival benefits of being born to a young mother are observed only when the mother is younger than 25 years," Gavrilova reported at a meeting last Sunday of the Gerontological Society of America. "This may have important social and actuarial implications, because so many women now decide to postpone childbearing due to career demands."

Here we go again. Not only do we risk infertility and birth defects if we try to have a kid past 35, now we can feel bad about our children dying "young" because we spent our early 20s not procreating but monkeying around in graduate school or trying to rise out of entry-level jobs.

So in case you missed the memo the first 400 times: Tick tock, ladies!

Will women never escape being told what is the proper age to make major life decisions? Even though nearly 40 years have passed since feminism entered the national consciousness, we're still governing much of our lives based not on what's best for us but on whether there is a culturally sanctioned, scientifically proven window of opportunity to do what we think we're supposed to do. The result is that the game of femaleness, like the game of football or basketball, is ruled by the clock.

And I'm not just talking about the biological clock. Long before most women have an ounce of concern about the viability of their eggs, they've been well informed of the pitfalls of not planning. Delay college too long, we're told, and you'll wind up answering phones about the time you should be getting your own office. Settle down before you're 28 and you'll have cheated yourself of the all-important "experimental phase," (promiscuity? a switch in sexual orientation? dating a drummer?) which, in certain circles, is considered a prerequisite to finding someone reasonable. Put off permanent commitment until your mid-30s, however, and you're dealing with a very limited pool of potential mates.