Listen to a successful woman discuss her failure to bear a child, and the grief comes in layers of bitterness and regret. This was supposed to be the easy part, right? Not like getting into Harvard. Not like making partner. The baby was to be Mother Natur e's gift. Anyone can do it; high school dropouts stroll through the mall with their babies in a Snugli. What can be so hard, especially for a Mistress of the Universe, with modern medical science devoted to resetting the biological clock? "I remember sitt ing in the clinic waiting room," recalls a woman who ran the infertility marathon, "and a woman-she was in her mid-40s and had tried everything to get pregnant-told me that one of the doctors had glanced at her chart and said, 'What are you doing here? Yo u are wasting your time.' It was so cruel. She was holding out for that one last glimpse of hope. How horrible was it to shoot that hope down?"

The manner was cold, but the message was clear-and devastating. "Those women who are at the top of their game could have had it all, children and career, if they wanted it," suggests Pamela Madsen, executive director of the American Infertility Associatio n (A.I.A.). "The problem was, nobody told them the truth about their bodies." And the truth is that even the very best fertility experts have found that the hands of the clock will not be moved. Baby specialists can do a lot to help a 29-year-old whose tu bes are blocked or a 32-year-old whose husband has a low sperm count. But for all the headlines about 45-year-old actresses giving birth, the fact is that "there's no promising therapy for age-related infertility," says Dr. Michael Soules, a professor at the University of Washington School of Medicine and past president of the American Society for Reproductive Medicine (asrm). "There's certainly nothing on the horizon." This means, argues economist Sylvia Ann Hewlett in her new book, Creating a Life: Professional Women and the Quest for Children (Talk Miramax Books), that many ambitious young women who also hope to have kids are heading down a bad piece of road if they t hink they can spend a decade establishing their careers and wait until 35 or beyond to establish their families. Even as more couples than ever seek infertility treatment-the number of procedures performed jumped 27% between 1996 and 1998-doctors are lear ning that the most effective treatment may be prevention, which in this case means knowledge. "But the fact that the biological clock is real is unwelcome news to my 24-year-old daughter," Hewlett observes, "and she's pretty typical."

Women have been debating for a generation how best to balance work and home life, but somehow each new chapter starts a new fight, and Hewlett's book is no exception. Back in 1989, when Felice Schwartz discussed in the Harvard Business Review how to creat e more flexibility for career women with children (she never used the phrase Mommy Track herself), her proposals were called "dangerous" and "retrofeminist" because they could give corporations an excuse to derail women's careers. Slow down to start a fam ily, the skeptics warned, and you run the risk that you will never catch up.

And so, argues Hewlett, many women embraced a "male model" of single-minded career focus, and the result is "an epidemic of childlessness" among professional women. She conducted a national survey of 1,647 "high-achieving women," including 1,168 who earn in the top 10% of income of their age group or hold degrees in law or medicine, and another 479 who are highly educated but are no longer in the work force. What she learned shocked her: she found that 42% of high-achieving women in corporate America (def ined as companies with 5,000 or more employees) were still childless after age 40. That figure rose to 49% for women who earn $100,000 or more. Many other women were able to have only one child because they started their families too late. "They've been m aking a lot of money," says Dr. David Adamson, a leading fertility specialist at Stanford University, "but it won't buy back the time."

Recent Census data support Hewlett's research: childlessness has doubled in the past 20 years, so that 1 in 5 women between ages 40 and 44 is childless. For women that age and younger with graduate and professional degrees, the figure is 47%. This group c ertainly includes women for whom having children was never a priority: for them, the opening of the work force offered many new opportunities, including the chance to define success in realms other than motherhood. But Hewlett argues that many other women did not actually choose to be childless. When she asked women to recall their intentions at the time they were finishing college, Hewlett found that only 14% said that they definitely did not want to have children.

For most women Hewlett interviewed, childlessness was more like what one called a "creeping nonchoice." Time passes, work is relentless. The travel, the hours-relationships are hard to sustain. By the time a woman is married and settled enough in her care er to think of starting a family, it is all too often too late. "They go to a doctor, take a blood test and are told the game is over before it even begins," says A.I.A.'s Madsen. "They are shocked, devastated and angry." Women generally know their fertil ity declines with age; they just don't realize how much and how fast. According to the Centers for Disease Control, once a woman celebrates her 42nd birthday, the chances of her having a baby using her own eggs, even with advanced medical help, are less t han 10%. At age 40, half of her eggs are chromosomally abnormal; by 42, that figure is 90%. "I go through Kleenex in my office like it's going out of style," says reproductive endocrinologist Michael Slowey in Englewood, N.J. 

Hewlett and her allies say they are just trying to correct the record in the face of widespread false optimism. Her survey found that nearly 9 out of 10 young women were confident of their ability to get pregnant into their 40s. Last fall the a.i.a. conducted a fertility-awareness survey on the women's website iVillage.com. Out of the 12,524 respondents, only one answered all 15 questions correctly. Asked when fertility begins to decline, only 13% got it right (age 27); 39% thought it began to drop at 40. Asked how long couples should try to conceive on their own before seeking help, fully 42% answered 30 months. That is a dangerous combination: a couple that imagines fertility is no problem until age 40 and tries to get pregnant for 30 months before seeing a doctor is facing very long odds of ever becoming parents.

In one sense, the confusion is understandable: it is only in the past 10 years that doctors themselves have discovered the limitations. "I remember being told by a number of doctors, 'Oh, you have plenty of time,' even when I was 38," says Claudia Morehead, 47, a California insurance lawyer who is finally pregnant, using donor eggs. Even among fertility specialists, "it was shocking to us that ivf didn't work so well after age 42," admits Dr. Sarah Berga, a reproductive endocrinologist at the University of Pittsburgh School of Medicine. "The early '90s, to my mind, was all about how shocked we were that we couldn't get past this barrier." But even as doctors began to try to get the word out, they ran into resistance of all kinds.

One is simply how information is shared. Childlessness is a private sorrow; the miracle baby is an inevitable headline. "When you see these media stories hyping women in their late 40s having babies, it's with donor eggs," insists Stanford's Adamson, "but that is conveniently left out of the stories." The more aggressive infertility clinics have a financial incentive to hype the good news and bury the facts: a 45-year-old woman who has gone through seven cycles of ivf can easily spend $100,000 on treatment. But even at the best fertility clinics in the country, her chance of taking a baby home is in the single digits.

In hopes of raising women's awareness, asrm launched a modest $60,000 ad campaign last fall, with posters and brochures warning that factors like smoking, weight problems and sexually transmitted infections can all harm fertility. But the furor came with the fourth warning, a picture of a baby bottle shaped like an hourglass: "Advancing age decreases your ability to have children." The physicians viewed this as a public service, given the evidence of widespread confusion about the facts, but the group has come under fire for scaring women with an oversimplified message on a complex subject. "The implication is, 'I have to hurry up and have kids now or give up on ever having them,'" says Kim Gandy, president of the National Organization for Women. "And that is not true for the vast majority of women." Gandy, 48, had her first child at 39. "It was a choice on my part, but in most ways it really wasn't. It's not like you can create out of whole cloth a partner you want to have a family with and the economic and emotional circumstances that allow you to be a good parent. So to put pressure on young women to hurry up and have kids when they don't have those other factors in place really does a disservice to them and to their kids."

To emphasize a woman's age above all other factors can be just one more piece of misleading information, Gandy suggests. "There are two people involved [in babymaking], and yet we're putting all the responsibility on women and implying that women are being selfish if they don't choose to have children early." She shares the concern that women will hear the research and see the ads and end up feeling it is so hard to strike a balance that it's futile to even try. "There is an antifeminist agenda that says we should go back to the 1950s," says Caryl Rivers, a journalism professor at Boston University. "The subliminal message is, 'Don't get too educated; don't get too successful or too ambitious.'" Allison Rosen, a clinical psychologist in New York City who has made it her mission to make sure her female patients know the fertility odds, disagrees. "This is not a case of male doctors' wanting to keep women barefoot and pregnant," she says. "You lay out the facts, and any particular individual woman can then make her choices." Madsen of A.I.A. argues that the biological imperative is there whether women know it or not. "I cringe when feminists say giving women reproductive knowledge is pressuring them to have a child," she says. "That's simply not true. Reproductive freedom is not just the ability not to have a child through birth control. It's the ability to have one if and when you want one." 

You can trace the struggle between hope and biology back to Genesis, when Abraham and Sarah gave thanks for the miracle that brought them their son in old age. "She was the first infertile woman," notes Zev Rosenwaks, the director of New York Presbyterian Hospital's infertility program. "It was so improbable that an allegedly menopausal woman could have a baby that her firstborn was named Isaac, which means 'to laugh.'" The miracle stories have fed the hope ever since, but so does wishful thinking. "It's tremendously comforting for a 34- or 36-year-old professional woman to imagine that she has time on her side," says Hewlett, which can make for resistance to hearing the truth.

This is the heart of Hewlett's crusade: that it is essential for women to plan where they want to be at 45 and work backward, armed with the knowledge that the window for having children is narrower than they have been led to believe and that once it begins to swing shut, science can do little to pry it open. And Hewlett argues as well that employers and policymakers need to do more to help families make the balancing act work. "The greatest choice facing modern women is to freely choose to have both, a job and a family, and be supported and admired for it, not be seen as some overweening yuppie." 

As it happens, Hewlett knows from personal experience. She says she didn't set out to write about how hard it is for professional women to be moms. She planned to do a book celebrating women turning 50 at the millennium and to look at what forces had shaped their lives. Then she discovered, in interview after interview with college deans and opera divas, a cross section of successful women in various fields, that none of them had children-and few of them had chosen to be childless. Many blamed themselves for working too hard and waiting too long-and waking up to the truth too late. "When I talked to these women," she recalls, "their sense of loss was palpable."

Hewlett had spent most of her professional life writing and lecturing on the need for business and government to develop more family-friendly workplaces; she has a Ph.D. in economics from Harvard. And she has had children and lost them and fought to have more. As a young Barnard professor with a toddler at home, she lost twins six months into her pregnancy: If only, she thought, I had taken time off from work, taken it easier. A year and a half later, she writes, she was turned down for tenure by an appointments committee that believed, in the words of one member, that she had "allowed childbearing to dilute my focus." Hewlett was lucky: she went on to have three more children, including Emma, to whom she gave birth at 51 using her own egg and infertility treatments. Hewlett says she understands "baby hunger."

At least she understands it for women. Men, she argues, have an unfair advantage. "Nowadays," she says, "the rule of thumb seems to be that the more successful the woman, the less likely it is she will find a husband or bear a child. For men, the reverse is true. I found that only one-quarter of high-achieving men end up without kids. Men generally find that if they are successful, everything else follows naturally." But that view of men doesn't quite do justice to the challenges they face as well. Men too are working harder than ever; at the very moment that society sends the message to be more involved as fathers, the economy makes it harder-and Hewlett's prescription that women need to think about having their children younger leaves more men as primary breadwinners. They would be fathers as far as biology goes, but they wouldn't get much chance to be parents. "A lot of my friends who are men and have had families are now divorced," Stanford's Adamson admits. "When you ask them what happened, the vast majority will say, 'Well, I was never home. I was working all the time. I didn't pay enough attention to my family. I wish I had, but it's too late now.'"

Hewlett still insists that men don't face the same "cruel choices" that women confront. "Men who find that they have no relationship with their adult kids at least have a second chance as grandfathers," she argues. "For women, childlessness represents a rolling loss into the future. It means having no children and no grandchildren." While her earlier books are full of policy prescriptions, this one is more personal. She salts the book with cautionary tales: women who were too threatening to the men they dated, too successful and preoccupied, too "predatory" to suit men who were looking for "nurturers." The voices are authentic but selective; taken together, it is easy to read certain passages and think she is calling for a retreat to home and hearth, where motherhood comes before every other role.

Hewlett replies that she is simply trying to help women make wise choices based on good information. She is not proposing a return to the '50s, she says, or suggesting that women should head off to college to get their MRS. and then try to have children soon after graduation. "Late 20s is probably more realistic, because men are not ready to commit earlier than that. And the 20s still needs to be a decade of great personal growth." She recommends that women get their degrees, work hard at their first jobs-but then be prepared to plateau for a while and redirect their energy into their personal lives, with the intention of catching up professionally later. "You will make some compromises in your career. But you will catch up, reinvent yourself, when the time is right."

The problem is that Hewlett's own research argues otherwise: in her book all of the examples of successful women who also have families gave birth in their 20s. These women may escape the fate of would-be mothers who waited too long, but they encounter a whole different set of obstacles when it comes to balancing work and family. Biology may be unforgiving, but so is corporate culture: those who voluntarily leave their career to raise children often find that the way back in is extremely difficult. Many in her survey said they felt forced out by inflexible bosses; two-thirds say they wish they could return to the work force. Much would have to change in the typical workplace for parents to be able to downshift temporarily and then resume their pace as their children grew older. Hewlett hopes that the war for talent will inspire corporations to adopt more family-friendly policies in order to attract and maintain the most talented parents, whether male or female. Many of her policy recommendations, however, are unlikely to be enacted anytime soon: mandatory paid parental leave; official "career breaks" like the generous policy at IBM that grants workers up to three years' leave with the guarantee of return to the same or a similar job; a new Fair Labor Standards Act that would discourage 80-hour workweeks by making all but the very top executives eligible for overtime pay.

Hewlett calls herself a feminist, but she has often crossed swords with feminists who, she charges, are so concerned with reproductive choice that they neglect the needs of women who choose to be mothers. In the history of the family, she notes, it is a very recent development for women to have control over childbearing, thanks to better health care and birth control. But there's an ironic twist now. "In just 30 years, we've gone from fearing our fertility to squandering it-and very unwittingly." The decision of whether to have a child will always be one of the most important anyone makes; the challenge is not allowing time and biology to make it for them. Reported by Janice M. Horowitz, Julie Rawe and Sora Song/New York