We often need to respond to, “How does my age impact on my chances for a healthy and successful pregnancy?” It is a question asked of obstetricians as more and more women are choosing to conceive after the age of thirty-five. It is not always easy to do because fertility rates decrease with age, but it happens with increasing frequency as fertility treatment becomes more sophisticated and successful.
You may be interested to know that prior to 1975, the peak years for women to have babies were between their twentieth and twenty-ninth birthdays. Then, at the height of the “baby boom,” in 1975, the birth rate in the United States started downward. The major reason for the decline was the change in contraceptive practices. Many more married women of childbearing age were using contraception in the 1980s than in the 1960s. (Married women between ages thirty-five and forty-four use contraception less often than younger wives. When they do, they tend either to end fertility permanently, through sterilization, or to rely on nonmedical methods.)
Recently, however, the downward trend ended, as the large group of “baby boomers” began having babies at age thirty-five or older. “Late pregnancies” increased by a whopping 37 percent. This switch is the subject of several studies of women over age thirty-five, designed to learn whether there is an increased risk associated with pregnancy, childbirth, or the period of confinement after labor for this growing group of women.
Recently reported results suggest that the risk of some problems in pregnancy may increase in midlife and that hypertension, diabetes, preeclampsia (toxemia of late pregnancy that includes hypertension, albuminuria, and edema), and premature labor may be more common in women who give birth after the age of forty. Much of the time, however, these complications can be taken care of medically and usually do not increase mortality.
The increase in diabetes is understandable. We know that there is an increase in diabetes mellitus with age, and so this problem is more likely to appear in women over thirty-five. Yet, even with this increase in incidence of diabetes and hypertension, modern prenatal care should assure normal results for mother and baby as long as mother is healthy when the pregnancy begins. However, women with medical complications, such as chronic hypertension or diabetes mellitus before pregnancy, may find that these conditions tend to be aggravated. They could affect baby’s health and survival.
A frequently asked question is whether women over thirty-five are more likely to have smaller babies. The answer is “no.” According to various studies, there is an increased birth weight in babies delivered by older women.
Delivery itself is another matter. Generally, there are fewer vaginal deliveries after the age of forty. This increase in cesarean sections is apparent in most of the medical literature.
After the baby is born, there might be an increased risk to the mother of fever due to infection, or of blood clots and possibly pulmonary emboli. The incidence of these complications is not dramatic, however, and doctors generally can recognize and treat these problems effectively. As far as the baby is concerned, chromosomal abnormality is one of the major worries of women having later pregnancies. A direct correlation between the age of the mother and chromosomal abnormality does exist, particularly in the number of Down’s syndrome infants that are liveborn. At age twenty-five there is one Down’s syndrome birth in 1,200; this statistic increases to one in 365 at age thirty-five; it jumps to one in 32 at age forty-five.
When all other chromosomal abnormalities are included, the risks are even higher. A review of middle-trimester amniocentesis data reveals that the risk increases from 1.3 percent at age thirty-five to 1.9 percent at age forty, and to almost 10 percent beyond age forty.
The most recent best-controlled hospital-based studies suggest that women of advanced maternal age delivering under optimum conditions may be at no higher risk for adverse outcome than pregnancies in younger patients. There once was a term, the elderly prima gravida, which referred to a woman who had never had a child before age thirty-five. The term is obsolete! We believe that in the absence of underlying medical disorders, and assuming modern obstetric care including prenatal diagnosis, advanced age in itself only minimally increases pregnancy risks.