Advanced Maternal Age, or Pregnancy at Age 35 or Older

Women who are pregnant at age 35 or older are often referred to as “advanced maternal age.” These women may be told that they should have a labor induction or C-section at 39 weeks, solely because of their age.

This article was written by Rebecca Dekker, PhD, RN, APRN, Mimi Niles, CNM, MSN, MPH, PhD student, and Alicia A. Breakey, PhD. Published March 29, 2016, © Evidence Based Birth®,

Why is this important?

Over the past four decades, there has been a dramatic increase in the number of women having their babies at age 35 and older. In the U.S., this increase started in the mid-1970s and has continued to steadily rise over time. Today, 15% of women giving birth are 35 and older, up from 11% in 2002 and 8% in 1990 (Mathews and Hamilton 2014; Martin, Hamilton et al. 2003; Martin, Hamilton et al. 2015).

There has also been an increase in the number of first babies born to women who are 35 or older. These increases have been seen across all ethnic groups in the U.S. (Mathews and Hamilton 2014).

Today, 10% of babies in the U.S. were born to first-time mothers age 35 or older. The average age at first birth is now 26 years of age—a record high for the U.S.! Meanwhile, in 2013, both the teen birth rate and the birth rate for women in their twenties hit record lows (Martin, Hamilton et al. 2015).

Why is parenthood being delayed?

The trend to delay parenthood is happening all around the world.  The availability of birth control is partly responsible for women postponing parenthood. However, birth rates in younger women have also gone down in countries that do not use birth control, so we can’t isolate birth control as the main reason. It’s thought that, worldwide, there are other social and cultural factors that play a bigger role than contraception in the increasing age of pregnant women (Mills, Rindfuss et al. 2011). 

Reasons people delay pregnancy and parenthood include:

• Women are reaching higher educational levels (Mills, Rindfuss et al. 2011)
• More women in male-dominated fields that are not as understanding or supportive of motherhood (Mills, Rindfuss et al. 2011)
• Cultural and value shifts have led towards more women not feeling “ready” to have a child yet (Cooke, Mills et al. 2010)
• Lack of childcare, low benefit levels, and workplace policies that signal to women that they cannot be both a wage earner and a mother (Mills, Rindfuss et al. 2011)
• Divorce, going through multiple partners before settling down, and living together before marriage leads some people to delay parenthood (Mills, Rindfuss et al. 2011)
• Economic or housing uncertainty, unemployment, temporary work, or unstable labor markets (Mills, Rindfuss et al. 2011)

Fertility treatments are another reason that people are getting pregnant later in life.

Parents, doctors, and research scientists have been working together to overcome infertility since the late 1880s. As scientists got closer to success, a 1969 Harris poll showed that the majority of Americans believed in vitro fertilization (IVF) was against God’s will.

But by 1978, the year of the first “test tube baby,” another Harris poll found that the majority of Americans supported IVF and would be willing to try it under the right circumstances. And by 2004, more than half a million babies had been born by IVF.

So in summary, a combination of fertility treatment options, birth control options, and social and cultural factors have all come together to lead a rise in the rate of women who have babies at age 35 or older.

Terms

Advanced maternal age is sometimes defined as being 35 or older, and sometimes as being 40 or older. Since the 1950s and possibly earlier, the ages of 35 and 40 were used by researchers to label women as being advanced maternal age (AMA).

In addition to the term AMA, women who are 35 or older and pregnant for the first time have been referred to as an elderly primigravida or elderly primipara. Primigravida means a person who is “pregnant for the first time.” Primipara means a person who is “giving birth for the first time.” Nulliparous is another term that you may see, and this refers to a person who has not yet carried a pregnancy beyond 20 weeks.

Because the terms “elderly” and “advanced age” have negative connotations and (understandably) may be seen as insulting to some women, for the rest of this article we will simply refer to women in this category as being “35 or older.”

Chances of getting pregnant at 35 or older

As a woman ages, her fertility—the chance she will get pregnant—is reduced. On average, this decline begins slowly in the early thirties and speeds up in the late thirties and forties. When a female is born, she is born with all of the eggs she will ever have. It’s thought the decline in fertility with age is due to a decrease in the number of eggs remaining and a decrease in the quality of eggs (Rowe 2006).

In 1986, researchers carried out a classic study to find out how likely it is for women to get pregnant as they age. They looked at women who were receiving artificial insemination with donor sperm. This study design was important because some people argue that lowered fertility is related to a decrease in the amount of sex people have as they age. However, with this study, there is no way that frequency of sex could explain findings, since the male partners were sterile (Schwartz and Mayaux 1982).

The women received artificial insemination once a month for up to one year, or until they became pregnant. Most (74%) of the women under the age of 31 were pregnant within one year, but that number went down to 62% of women between 31 and 34, and 54% of women aged 35 and older.

Male fertility declines with age as well. Researchers have found strong evidence that as men age, they can expect a decline in sperm counts, semen volume, sperm motility, and the number of normal sperm. Older women with older male partners who are trying to get pregnant may experience the combination of female and male age-related fertility decline (Johnson, Dunleavy et al. 2015).