When an egg emerges from the ovary, it is surrounded by a protective layer called the zona pellucida. With older women, the covering is sometimes too dense to be shed after the egg is fertilized and prevents the embryo from implanting on the uterine wall.

While men experience some decline in the number of sperm, motility, and morphology—the number of normal sperm—after age 40, it’s generally not enough to prevent them from becoming fathers. There are typically 150 to 300 million sperm released in one ejaculation. Even if the number drops by 50 percent, there are still pretty good odds there will be some keepers.

And now, technology has advanced to the point where even men with extremely poor sperm quality can father children. With intracytoplasmic sperm injection, an embryologist can inject a single sperm into the cytoplasm of an egg with a microscopic needle while bypassing the normal cascade of chemical reactions necessary for fertilization.


The procedure, which has only been around since 1992, is a primary reason for the speed-of-light development of fertility treatment for aging would-be parents—because it’s not only sperm that can be injected into the egg. The processes of microinjection and micromanipulation of egg and sperm are making a wider array of new treatments possible.

DOUBLE TROUBLE: 

Since the advent of in vitro fertilization two decades ago, there has been an explosion in the number of multiple births, particularly among women over 40. Statistics released last September by the Centers for Disease Control reveal a 52 percent increase overall in twin births between 1980 and 1997. Among women between 40 and 44, the increase in the number of twins born was 63 percent, and among women between 45 and 49 it was a staggering 1,000 percent.

The ages of the mothers had less effect on the health or survival of the infants than the pregnancy complications generally associated with multiple births. For example, the risk of a very low birth weight is eight times higher for twins than for single births. The ultimate impact of multiple births on the lives of older parents is immeasurable. “Keeping up with two kids instead of one is a real challenge,” says Machelle Seibel. “The increase in energy required is exponential rather than additive.”

For example, embryologist Jacques Cohen, scientific director at the Institute for Reproductive Medicine and Science of Saint Barnabas in Livingston, New Jersey, has developed a procedure called cytoplasmic transfer that shows promise for assisting women approaching their early forties who either can’t get pregnant through in vitro fertilization or have embryos of such poor quality they don’t survive. Doctors take the cytoplasm of a youthful and healthy egg—containing not the dna but the proteins and enzymes for healthy cell growth—and inject it into the problematic egg to boost its quality. Possible health risks with the procedure have not yet been conclusively studied and there are troubling ethical questions. (See “Can a Baby Have Three Parents?” page 66.) But out of 26 attempts, the technique has resulted in 12 live births.

When San Franciscan Alison Carlson failed to get pregnant at 42, she says she worried she had a “defective body. Me, who could bench-press 190 pounds and choreograph the perfect tennis point.”

Jamie Grifo, director of New York University’s reproductive endocrinology unit, is further refining another technique to assist women between 42 and 45, whose chances of having a child with their own eggs hover around 5 percent. He takes an older woman’s egg and extracts the nucleus, which contains the dna. Then he removes the nucleus from the donor egg of a much younger woman and in its place microinjects the genetic material of the older woman. The procedure, attempted on two women last year, resulted in fertilized embryos but not babies. Grifo and his team went back to the lab, perfecting the process on mice. The result: baby mice.

Grifo’s groundbreaking work could provide the answer women like Alison Carlson are looking for. Carlson is a golden girl: blond, sunny, a former professional tennis coach in San Francisco. When she got married last year to a younger man and started trying to get pregnant at 42, she assumed she’d succeed quickly. “I was an athlete,” she says. “I felt the normal rules wouldn’t apply to me.” At first it seemed she would be right. In her initial round of in vitro fertilization, Carlson produced an impressive 27 eggs, and 25 were fertilized: “I was a champ.” She got pregnant but quickly miscarried. Forty-five percent of women over 40 do, usually because of chromosomal abnormalities in their eggs. “Suddenly I felt like I should buy one of these T-shirts that say ‘I Can’t Believe I Forgot to Have Children.’” Carlson says that when she tried again, she failed to get pregnant at all.

Intellectually, Carlson knows the problem is age, but emotionally she cannot accept it. Like so many men and women over 40 who begin fertility treatments, she feels pressure to keep trying. “I’m embarrassed because, first, I felt I was being so arrogant,” she says. “Like, here we all are, a bunch of baby boomers who went to college in the second wave of feminism, dedicated to having important careers before having babies, and then paying gobs of money so science can give us what we want. I’m appalled at my own sense of entitlement.”

Given the anguish many aging baby boomers now experience trying to get pregnant, it’s hard to fathom that the future holds no less than the end of infertility. Doctors recently discovered how to freeze a woman’s eggs when she’s young and then thaw them when she’s ready to get pregnant. A woman could finish college and graduate school, launch a career, and then start a family with eggs she parked on ice at age 18.

Left: Contemporary birth records of the Hutterites, a religious sect in the western U.S. and Canada that does not practice birth control, and seventeenth-century birth records from a French village reveal a similar pattern: Natural fertility rates among women drop off precipitously around age 40. The latest available overall birthrates for U.S. women follow the same downward trend but are lower across the board because of the prevalence of birth control and a tendency of women to marry later in life.

Right: Statistics indicate that the risk of women having children with chromosomal abnormalities, including Down’s syndrome, rises steadily from 2.1 per thousand births at age 25 to 53.7 per thousand births at age 45.

Banking individual eggs is just the beginning. Recently Kutluk Oktay, the chief of reproductive endocrinology and infertility at New York Methodist Hospital in Brooklyn, has been experimenting with freezing and transplanting swatches of ovarian tissue. Each bit of tissue contains thousands of immature follicle eggs. While individual, already-developed eggs die easily when frozen, immature follicle eggs embedded in the ovarian tissue fare a lot better. Oktay has already tried the technique on a 30-year-old dancer from Arizona who’d had her first ovary removed at 17 because of cysts but had the foresight to have her second ovary frozen. Last fall, Oktay sewed 80 small pieces of the tissue back into her pelvis and revived her menstrual cycle. The woman is not trying to conceive. But Oktay’s colleague, Roger Gosden, now reproductive biology research director of McGill University’s Royal Victoria Hospital in Montreal, has removed the ovaries of sheep, frozen them, thawed them, sutured them back in the sheep—and gotten lambs aplenty.