Babies Tale

Infertility and late motherhood are linked in two ways. First, many women come late to motherhood because they have had trouble conceiving. Second, fertility declines with age, and many women who leave childbearing to their mid- or late 30s or early 40s experience some difficulty in getting pregnant.

Although every doctor and medical textbook will state that fertility declines with age, finding out exactly when and how fast fertility declines is not so easy. Figures from the Office of Population Censuses and Surveys show that in I996, 400,8I0 women aged 35 to 39, and 74,643 women aged 40 to 49 gave birth, out of a total of 3,9I7,933 births for women of all ages-clearly a minority. This figure doesn’t really prove anything, however. The smallness of the figure may be due more to women choosing to have their babies earlier rather than experiencing difficulty in having them later. According to the Report of Final Nativity Statistics, I995 (National Center for Health Statistics), “Birth rates for women in their thirties is still increasing, but the pace has slowed. The birth rate for women aged 40 to 44 years rose 20% between I990 and I995, and increased 74% during I98I-95. The rising birth rate, along with the increasing number of women in this age group, has meant that there were more babies born in I995 to mothers in their forties than in any year since I966.”

A study by Professor James Trussel of Princeton University, published in I985, shows that between the years I550 and I849, when people did not have access to birth control, only about 7% of women who married young were infertile, while one-third of women who married at the age of 35 did not give birth and nearly 60% of women who married at 40 had no children.

When and how fast does fertility decline? One recent study to try to answer this question was carried out in the Netherlands on a group of 75I women attending clinics for artificial insemination by donated sperm. This study showed the decline in fertility began at the age of 3I, and that after this age the chance of conceiving per monthly cycle fell by about I2% with each year of age. The chance of a woman aged 35 getting pregnant and giving birth to a healthy baby was about half that of a woman aged 25. The study also showed that for older women, continuing beyond I2 cycles was important, since older women took longer to conceive. While 54% of women over 3I became pregnant after I2 cycles, 75% did after 24. These figures may be slightly different compared to those found from women who conceive normally, because we know there is a slightly lower rate of conception through donor insemination than natural conception. Still, they are likely not to be much different.

Older women tend to be infertile for the same reasons as younger women, but the problems arise more frequently. The most common reason is probably a failure to ovulate. As women age, they are likely to have more menstrual cycles without ovulating than younger women; eventually most cycles will be anovulatory (menstruation without releasing an egg). Women usually continue to have periods long after they cease to be fertile, for perhaps ten years before they reach menopause.

Older women are also more likely to have suffered from some infection or illness that might scar the Fallopian tubes, the second most common cause of female infertility. Older women are also more likely to develop fibroids or other uterine disorders that affect fertility.

Research into infertility and a host of new treatments have meant more women with fertility problems are able to have a baby than ever before. Advances such as IVF (in-vitro fertilization, the “test-tube baby” treatment) have put infertility very much in the public eye. Infertility is no longer the hush-hush issue it used to be. Because of this, many women are now aware their fertility may be a problem. They are much more likely to seek help quickly if they do not become pregnant soon after stopping contraception.

Women who have spent years on the Pill or worrying about contraception, who may never have had an act of unprotected intercourse or fretted till their period turned up if they did, may be surprised to find pregnancy does not automatically result as soon as they abandon contraception, In fact, it has been estimated that the average length of time for a fertile couple having regular sexual intercourse to conceive a baby is about six months. This means that for every lucky couple who gets pregnant the first month, another couple will wait a year. It’s a little like throwing the dice and getting the certain number you’re hoping for-your chances are the same for each throw, but over a number of throws, your number is more likely to come up.

Similarly, the chance of conceiving each month is probably the same, but for the woman in her late 30s, not conceiving right away will probably ring alarm bells. She will be aware all the time that a delay of a year in conceiving may considerably reduce her chances. She may rush off for fertility investigations before she has given her body a chance to conceive naturally.

If a couple has not conceived after a year, and especially if the mother is older, most doctors will go ahead and refer them to a fertility specialist. The specialist will decide if there is really a problem and what this might be.

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