The Medical Risks of Waiting

By Claudia Wallis

New techniques make it safe for older mothers

To a doctor, a woman pregnant for the first time after 35 is an "elderly primigravida." If that sounds unappealing, it may reflect the medical establishment's longtime disapproval of delayed motherhood. The traditional view was that pregnant women in their 30s were risky patients, complications could be expected, and a caesarean, many doctors thought, was pro forma.

Today that view has changed. "I even hate to use that term now," says Washington, D.C., Obstetrician William Gold. "We've learned that women over 35 can have normal pregnancies. Age is not necessarily a problem."

The reversal has come about because of changes both in medicine and in women. The boom in fitness programs has put women over 30 into better shape than ever before. At Baylor College of Medicine, Obstetrician Robert Franklin sees would-be mothers at 40 "in fabulous condition. They're in better health than many younger women." The popular concern for good nutrition has also made a difference. According to Reproductive Biologist Cecil Jacobson, improved diets help "conserve reproductive capacities."

Still, when a woman postpones child bearing, she increases the chance that she will not be fit when the time comes. "Her gamble," says Chicago Ob-Gyn Allan Charles, "is that she won't have diabetes or high blood pressure." Or, for that matter, arthritis, respiratory ailments, obesity or kidney disease. All of these conditions make pregnancy more difficult. Diabetes and hypertension, for example, can interfere with the normal development of the placenta. Though some of these ailments can be controlled by diet and medication, their incidence increases with age.

So does the rate of birth defects. A woman is twice as likely to give birth to a defective child at age 40 as she was at 25 and five times as likely after 45. One possible explanation is aging eggs. A human female is born with about 2 million immature eggs, or ooecytes. Between puberty and menopause about 400 of them will mature into fertile eggs, a process that involves halving the number of chromosomes during cell division. According to theory, the older the ooecyte when it undergoes division--and in a 40-year-old it has been exposed for twoscore years to pollution, pesticides and X rays--the greater the likelihood that something will go wrong in the process. The most frequent error: an extra chromosome in the egg nucleus. The extra chromosome is usually number 21, which leads to Down's syndrome, a form of mental retardation. (Researchers have found, however, that in 25% of the cases, this defect can be traced to the father.)

Today doctors are able to detect Down's syndrome and more than 100 other birth defects with amniocentesis, a test that is modern medicine's biggest boon to older mothers. It is performed around the 14th or 15th week of pregnancy, at a cost of about $500. The procedure calls for the insertion of a long thin needle into the abdomen in order to extract a sample of amniotic fluid, the liquid that cushions the fetus. An ultrasonic scan of the uterus is generally used to ensure that the needle does not puncture the placenta or injure the fetus. Fetal cells in the fluid are then grown in a laboratory for two to four weeks, studied for chromosomal abnormalities, and, in some cases, checked for such metabolic disorders as Tay-Sachs disease. The fluid portion of the sample is tested for alpha fetoprotein. High levels of this protein can be a sign of spinal cord or brain defects.

Amniocentesis does not pick up all birth defects. Cautions Dr. Richard Morton, associate medical director for the March of Dimes: "Defects caused by the interplay of environmental and genetic factors--cardiac and intestinal defects, cleft lip and palate, club foot--are missed." The procedure also carries a slight risk of infection or other complications that could lead to miscarriage. Still, for many women over 35, the option to detect and then abort a severely deformed fetus is well worth the risk.

Older mothers also face a mortality rate that edges higher with each birthday. In the U.S., fewer than one out of 10,000 women giving birth die (the 16th lowest in the world). But women from 35 to 39 have five times the risk of women in their early 20s. They also face twice the risk of miscarriage. Nevertheless, many older women would be delighted to take their chances, if they could just get pregnant. That too becomes more difficult after 35.

One reason is that ovulation becomes more sporadic. A woman may continue to have 13 menstrual cycles a year, but, says Morton, "there is evidence that after 35 not every cycle is ovulatory." An older woman is also more likely to have had gynecological disorders that interfere with conception. Among them: pelvic infection and tubal damage, which can be caused by sexually transmitted diseases and exacerbated by intrauterine devices (I.U.D.s); benign fibroid tumors, which can interfere with the implantation of a fertilized egg; and endometriosis, in which the lining of the uterus has escaped into the pelvic cavity.

Antipregnancy measures, taken years earlier, may haunt the would-be mother. Two or more abortions raise the probability of infertility and can make miscarriage two or three times more likely. The use of birth control pills can have a "shadow effect"--it may take a year or two for the pill-free woman to restore her fertility.

There is no question, however, that women in their late 30s and 40s are getting more help. About half of those with fertility problems can be successfully treated with surgery or drugs. Difficult deliveries can be aided with advanced monitoring devices. When treatment succeeds, the fruits of labor are sweet. Says Houston's Dr. Franklin of new mothers in their mid-40s: "They are the happiest people you ever saw." --By Claudia Wallis. Reported by Adrianne Jucius/New York

With reporting by Adrianne Jucius/New York

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