Guest Post by KG Anderson, Ph.D.

Last week's Stepmonster piece focused on reactions to the news that actress Kelly Preston is pregnant at age 47, raising questions about the consequences for women of extending their reproductive lifespans. If more women had babies at later ages, would this "level the playing field" for women? Would some of the tradeoffs women experience between work, romance and family cease to exist? Wednesday has asked me, as an anthropologist and evolutionary biologist, to chime in with a few thoughts on this topic. (Some of the material presented here is discussed in more detail in my book Fatherhood: Evolution and Human Paternal Behavior, co-authored with Peter Gray.)

First, a question: Just how common it is for older women to have babies? High profile older celebrity moms including Preston create the impression that there's a virtual baby boom going on among older women. On the other hand, you are quite likely to know women who have encountered difficulties conceiving or carrying a pregnancy. You may even have experienced this firsthand. Many women have discovered that having a baby past a certain age is not easy.
While many people leap to the conclusion that celebrity older moms like Kelly Preston must have resorted to expensive assisted reproductive technologies, several comments on last week's Stepmonster entry were from women who got pregnant in their late 40s with no medical assistance. If we look at the raw numbers, we see that older women can--and do--have babies.

Yet demographically they're a drop in the bucket, overwhelmed by the sheer numbers of babies born to younger women. Data on age-specific fertility rates in the United States from 2000 to 2005 suggest that only 0.12% of babies born to American women are to moms ages 45-49. Put another way, that means for every 1000 babies born in the US, only 12 are born to women in their late 40s. (In contrast, 281 of those thousand babies are born to women ages 25 to 29, the peak years of U.S. fertility, and 766 are born to women ages 20 through 34.)

The raw data do not address how many of those older moms got pregnant naturally versus through medical assistance. If we look at cultures that do not have access to assisted reproductive technologies, or to reliable birth control, we see that older women were definitely having kids in non-industrialized societies. Kim Hill and Magdalena Hurtado have provided detailed demographic data on the Ache, a group of hunter-gatherers living in Paraguay. Their data reveal that 4.29% of births occur to women ages 45 to 49. That's lower than any other age group in their sample (apart from 10 to 14 year olds), but the data demonstrate that hunter-gatherer women in their late 40s were not wholly sterile.

Even if medical science can extend women's reproductive years, and perhaps even end the ticking of the biological clock entirely, I suspect most women would not take advantage of the opportunity to have babies in their late 40s, 50s or even 60s. Most women have all the kids they want by their mid-40s--and a surprisingly large fraction take surgical steps to ensure that they won't have any more. A 2005 CDC study of reproductive health patterns of American women found that 52% of women ages 40-44 had undergone surgical sterilization. This includes hysterectomies (12% of women), which are often performed for medical reasons and not for limiting fertility - but fully a third of women (33.6%) had undergone tubal sterilization, a procedure that over 90% report having because they already had all the children they want. Thus, at least a third of women in their early 40s are so committed to not having more children that they have had their tubes tied.

However, the authors of the report also note that the percentage of women who have undergone surgical sterilization has declined dramatically since 1995, when 66% of women ages 40-44 reported any sterilizing operations. They attribute this decrease to "the overall patterns of delayed childbearing among women 15-44 years of age, which result in lower proportions of older women being ready to adopt permanent forms of contraception." Thus, while a slim majority of women in their 40s are taking permanent steps to prevent future pregnancies, the number doing so is declining. More women are at least keeping the window of future fertility open.

Last week's Stepmonster blog raised the question of whether, if later reproduction became more commonplace, it might change the dynamics of male/female relationships, for example by increasing women's status in the sexual marketplace and allowing them to compete with younger women for partners in ways they couldn't before. I personally doubt that it will completely level the playing field. Perhaps if all women adopted late reproduction, older and younger women would be on equal footing - but there will always be women wanting to have kids in their 20s and 30s, and men willing to father those children. And one might argue that there are many benefits to having kids earlier in life - or at least not delaying your first reproduction too long. Older moms have increased risk of birth defects, for example, and many people express concerns about reaching retirement age when your child is still in high school (what if my health declines as I age? How can we afford to retire when there's college to pay for?).

Nevertheless, there are certainly some women who will be willing to have a baby at older ages. First, some women put off trying to have a family until they are older because of the demands of education, career, finding the right partner, etc. (As an academic, I have many colleagues who simply felt they could not have kids until they had tenure or were well on their way to tenure.) Second, there are women who have personal histories of fertility problems; they may have tried unsuccessfully to have a baby at younger ages, and they are still trying in their 40s. These are the women for whom medical assistance might hold out the most hope - but some of these women will not achieve their goal of having a biological baby.

The third group includes women who already have children, and want an additional baby later in life. It is worth noting that this group includes women who have repartnered at an older age. A growing fraction of Americans will experience several significant unions throughout their lives , either marriages or cohabitational relationships. By their 40s, many people will find themselves in new relationships, often with one or both partners bringing children from previous unions. (This is, after all, a blog about stepmothers.) I knew a woman years ago who had several half siblings, and her mother had given her this piece of advice: "Never marry more than once, because each time you do, he'll want you to have his baby." And indeed this is a common pattern; my colleague Susan Stewart had found that couples with stepchildren often have a child together as a means of strengthening their own identity as a family and reinforcing their own relationship.

Celebrity older moms like Kelly Preston raise questions about the appropriateness and acceptability of fertility at older ages, and attract attention because later fertility is viewed as unusual, perhaps even wrong. The evidence suggests that while it's relatively uncommon, and not desired by most women, having a baby in your late 40s is biologically feasible (at least for some women), and desirable for a growing fraction of women. The time may come when an actress or musician who gets pregnant past 45 will no longer be considered a newsworthy event.

Recent Posts in Stepmonster

Why Do We Send Our Kids to Sleepaway Camp?

The real reasons we send our kids to camp will probably surprise you.

The One Topic American Parents Need to Discuss but Aren't

Whether the Kaufmans were foolish or not isn't even the main point.

Why Do We Send Photos of Our Kids as Holiday Cards?

Holiday cards are artifacts that express our beliefs about childhood and parents

Everything You Think About Mothers and Childhood Is Wrong

Sure that, thanks to experts, we're raising our kids "right"? Guess again

Step Back, Stand Down, Befriend Your Kid's College Advisor

Lacy Crawford, author of Early Decision, analyzes school application insanity

Feathers and Fendi: Understanding Fashion Week

What the rites of Fashion Week tell us about Manhattan, the Fashion Tribe and us