Does the ‘fertility cliff’ really happen at age 35? What new studies say

Giving birth at or after this age will cause doctors to say you are of “advanced maternal age.” This term is a more modern and sensitive version of the old nomenclature: geriatric pregnancy.

Fertility doctors and researchers say many women consider age 35 a turning point. After that, according to this theory, pregnancy and continuing the pregnancy until its end becomes very difficult.

This general line of thinking is widespread. But this is not entirely true.

For University of South Carolina sociologist Emily Mann, the concept of the “fertility gap” has gained a great deal of attention, especially in the American imagination, since the 1970s.

“It’s like a buzzword,” he adds.

However, more and more women aged 35 and over are becoming pregnant. Data from the U.S. Centers for Disease Control and Prevention (CDC), released in July, showed that although the U.S. total fertility rate would decline in 2024 — with 53.8 births per 1,000 women of reproductive age — rates for women giving birth between the ages of 35 and 39 remained stable. The birth rates of women over the age of forty increased by 2%, according to the data.

This may be, at least in part, a result of changing economic and social trends. More women say they are delaying pregnancy because they are not yet able to raise children, or because they want to complete their studies and pay for school, or because they want to find a suitable partner. As assisted reproductive techniques improve, more women are turning to procedures such as in vitro fertilization, which allows them to become pregnant at an older age.

— We know that, in general, pregnancy is much easier for a younger woman than for an older woman. But this is demographic data. This does not necessarily indicate, individually in each case, how difficult or easy it is – says Dr. Mann

Age is the main factor that causes infertility. “This is indisputable,” said Dr. Francesca Duncan, assistant professor of obstetrics and gynecology at Northwestern University. Researchers generally define infertility in people under 35 as the inability to conceive after a year of trying.

But fertility doesn’t suddenly decline at age 35. It depends on a complex set of factors — for both women and men.

Why did 35 become a non-magical number?

Historically, 35 was the age at which doctors determined that a woman’s risk of having a fetus with a chromosomal abnormality was roughly equal to her risk of miscarriage after amniocentesis — a procedure that can detect some of these abnormalities.

The idea that 35 is a magic number has become established, Dr. Duncan said.

The risk of pregnancy with a chromosomal abnormality or miscarriage generally increases with age. But after age 35, this risk increases. The annual increase in risk is much greater between ages 35 and 40 than it is between age 25, said Dr. Natalie Clark Stentz, medical director of the Center for Reproductive Medicine at University of Michigan Health.

Data on fertility outcomes vary. According to the American College of Obstetricians and Gynecologists (ACOG), a woman’s chance of getting pregnant in one menstrual cycle is about 25% to 30% for healthy couples in their 20s or 30s. By age 40, a woman’s chance of getting pregnant is less than 10% in each menstrual cycle.

How does a woman’s fertility change with age?

Ovarian reserves decrease and quality deteriorates

Women are born with a certain number of eggs — approximately 1 to 2 million eggs — which die with age.

The American College of Obstetricians and Gynecologists states that a woman’s peak reproductive potential occurs between the end of adolescence and the end of her twenties. As the age of 35 approaches, egg loss accelerates every year. By age 37, a woman has about 25,000 eggs remaining.

But the speed at which these eggs are consumed varies from person to person. For example, chemical components found in cigarette smoke can accelerate egg loss. Metabolic conditions such as obesity and diabetes can also contribute to low reserves.

Researchers are increasingly studying the influence of genetics on ovarian reserves. If a woman’s mother gives birth at age 40, for example, that doesn’t guarantee that she will also be able to get pregnant at that age — but it may increase the likelihood of pregnancy somewhat, Dr. Stentz said.

Egg quality also affects fertility. As a woman ages, the quality of her remaining eggs declines.

As a woman ages, her ovaries gradually produce lower levels of estrogen and progesterone, making pregnancy difficult and eventually leading to menopause.

“Every decade, your cycles change,” says Dr. Mary Rosser, director of Integrative Women’s Health at Columbia University Irving Medical Center. “Hormones change and this also reduces fertility.

Other complications related to aging

The older a woman gets, the more likely she is to develop a range of other conditions that can make pregnancy difficult. For example, fibroids — tumors in the uterus that can cause infertility — are most common in women between the ages of 30 and 50.

The risk of diabetes, obesity and infertility-related autoimmune diseases also increases with age.

What happens to men’s fertility as they age?

Researchers have paid less attention to how men’s fertility declines with age, but men also have more difficulty conceiving as they age. They produce new sperm throughout their lives, but when they reach age 40, their testosterone levels decline and they produce progressively worse quality sperm. In addition, as you age, sperm can undergo subtle changes in shape, making it more difficult for them to move and fertilize eggs.

Just like women, men are more likely to develop chronic diseases such as diabetes and high blood pressure as they age, which can make pregnancy difficult.

Scientists are learning more about behavioral factors that may contribute to male infertility, including marijuana use.

Although some researchers say focusing on a specific age can be misleading, it still influences the way we think about fertility care. Doctors recommend that after six unsuccessful months, women over 35 who have tried to conceive seek an infertility evaluation.

This number remains a historical and practical marker, not a biological limit, Dr. Rosser said.