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

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