Considering Parenting

Aging and Fertility

For various reasons, including access to birth control, more career and educational opportunities, and economic concerns, more women in the United States are delaying childbearing. Today about one in five women has a first child after age thirty-five.¹

Many women who try to have a baby in their mid- and late thirties or early forties have no problem getting pregnant. Yet fertility does decline as we age, and many other women struggle to get pregnant or are unable to get pregnant or carry a pregnancy to term. This reality can put us in a bind: We may feel unready to have a baby now while also concerned about not being able to become pregnant later. For these reasons, it’s important to understand the effect aging has on chances of conceiving and carrying a pregnancy to term.

During any given menstrual cycle, a twenty-five-year-old woman has about a 25 percent chance of becoming pregnant. This percentage begins to drop in the late twenties and decreases more significantly in the mid- and late thirties, until by age forty a woman has about a 5 percent chance of conceiving per cycle.²

These statistics sound more alarming than they are, though. A younger woman is not five times more likely to conceive than a woman of forty; she is simply more likely to get pregnant in fewer cycles. Over the course of a year, a woman who is between the age of thirty-five and thirty-nine has approximately a 60 percent chance of spontaneously conceiving (with no fertility interventions). The rate jumps to 85 percent after two years.³

Age affects our ability not only to conceive but also to carry a pregnancy to term. Chromosomal abnormalities, the cause of more than half of all miscarriages, are more likely as we age. A woman in her twenties has a 12 to 15 percent chance of having a miscarriage each time she becomes pregnant, while a woman in her forties has close to a 50 percent risk of miscarriage.

Statistics provide valuable information on the likelihood of conceiving and/ or carrying a pregnancy to term. They cannot, however, predict what will happen for any individual woman. In addition, decisions about when to try to become pregnant, especially as we get older, are often complicated by factors that have little to do with age. Many of us put off having children because we don’t feel emotionally or financially ready or because we don’t have a partner and don’t want to be a single parent. Yet waiting means that we may be unable to get pregnant when we are ready. Recognizing this reality in no way diminishes the importance or value of education, career, or other life choices that lead us to postpone childbearing, but it places front and center how difficult it can be to make decisions and compromises about when to try to get pregnant.

Excerpted from the 2011 edition of Our Bodies, Ourselves. © 2011, Boston Women's Health Book Collective.