According to an article published in the Nov. 4, 2005 issue of the New England Journal of Medicine, the past decade has seen a remarkable shift in the demographics of childbearing in the United States. The number of first births per 1,000 women 35 to 39 years of age increased by 36 percent between 1991 and 2001, and the rate among women 40 to 44 years of age increased by a remarkable 70 percent. Additionally, in 2002, 263 births were reported in women between 50 and 54 years of age.
Most media attention paid to older moms has been favorable, inspiring a female business-school student who declared on a nationally televised segment of CBS's 60 Minutes (entitled "The Biological Clock"), "I plan to be super fit, super in shape when I'm 40, 50. And if I'm physically able to do it, then I will have a child at 55."
Yet, how old is too old, and how realistic is it for a young woman today to expect to delay her childbearing into the later decades of her life?
You can be healthy, but fertility still decreases
Yes we do have the technology to help older women achieve pregnancy, yet there are much higher risks associated with advanced maternal age.
The effect of maternal age on the outcome of pregnancy is best assessed by examining the source of the risks: those associated with using older eggs and those from having an older "carrier." Egg issues result in declining fertility, miscarriage and babies with chromosomal abnormalities such as Down's syndrome. Carrier issues include gestational diabetes, hypertensive complications and stillbirth.
So what about the notion of delaying childbirth until a maternal age of 45, 50 or older?
In my program there is currently no cut-off age for a woman requesting assisted reproductive procedures to get pregnant. Many programs do use a cutoff age which is usually arbitrarily determined by the doctor. I feel that this is age discrimination since there are no studies that indicate that there is a specific age beyond which pregnancy should not be attempted.
If a program has a cutoff age of 45, can the doctor tell the 46 year old that her risks are appreciable different from the 45 year old? They can't.
Patients and their partners should be informed about the potential risks and allowed to make their own decisions about treatment just like they do in all other areas of medicine.
An older woman who wants to attempt pregnancy using her own eggs can reduce the risks associated with older eggs by attempting pregnancy using in vitro fertilization with preimplantation genetic diagnosis (PGD). PGD can screen out most of the chromosomal abnormalities which may occur in older eggs.
Compared to in vitro fertilization without PGD, the chance for pregnancy can be increased 15 to 20 percent and the risk for miscarriage decreased by 50 percent or more. The risk for delivering a baby with Down Syndrome can almost be eliminated.
Alternatively, older women can use eggs donated from a younger woman. Pregnancy rates among older women who choose this route are excellent, with the risks of both miscarriage and chromosomal abnormalities consistent with the age of the donor, rather than the recipient. These women are still subjected to the same "carrier" risks however, consistent with their own age.
So how can we advise young career-minded women when she asks about her choices in regard to fertility?
Generally speaking, the decade between 25 and 35 years of age would seem to be ideal. A woman's education is typically complete, she has usually gained some experience in her professional arena, and pregnancy is at its safest.
For women between 35 and 45 years of age for whom earlier childbearing is not an option, this decade remains safe enough that maternal age alone should not be a contraindication to childbearing. However, women do face decreasing fertility and an increase in the risks of miscarriage and chromosomal abnormalities. Perimenopausal and postmenopausal pregnancy remains an option for those women who are lucky enough to find themselves healthy and sufficiently wealthy to pursue it, and who are willing to assume the risks involved.