NEW YORK.- One number is essential if you want to have children: 35.
If you give birth at this age or later, doctors say you are pregnant “advanced maternal age”. This term is a newer, weaker version of an older term: “geriatric pregnancy.”
Fertility doctors and researchers say many women consider the age of 35 to be old a turning point. From this age, the theory goes, it is very, very difficult to get pregnant and carry the pregnancy to term.
This way of thinking is widespread. But it’s not entirely true.
The concept of “Fertility Cliff”According to Emily Mann, a sociologist at the University of South Carolina, “It’s really taken hold since the 1970s – and especially in the American imagination.”
“It’s like a catchphrase,” he added.
However, more and more women aged 35 and over are becoming pregnant. Data from the Centers for Disease Control and Prevention released in July showed that while the total fertility rate in the U.S. declined in 2024, at 53.8 births per 1,000 women of childbearing age, birth rates for women ages 35 to 39 remained stable. And rates among those over 40 rose 2%, according to the data.
This may be at least partly due to this changing trends economically and socially. More and more women say they are waiting to get pregnant because they cannot yet afford to raise children, because they want to finish their studies and recoup the costs of studying, or because they want to find the right partner. And as assisted reproductive technologies have improved, more women have turned to procedures such as in vitro fertilization, which can help them conceive at an older age.
“We know that it is generally easier for a young woman to become pregnant than for an older woman,” Mann said. “But they are Population level data. “It doesn’t necessarily tell you as an individual how difficult or easy it can be.”
Age is the main factor that determines infertility. “It’s undeniable,” said Francesca Duncan, associate professor of obstetrics and gynecology at Northwestern University. Researchers typically define infertility in people under 35 as not becoming pregnant after a year of trying.
But fertility doesn’t suddenly drop when you reach this age. It depends on a number of complex factors, both in women and men.
Historically, the age at which doctors discovered this was 35 years old the risk A woman’s risk of having a fetus with a chromosomal abnormality was about the same as her risk of miscarriage after amniocentesis, a procedure that can detect some of these abnormalities.
“It seemed like 35 was this magic number,” Duncan said.
The risk of pregnancy with a chromosomal abnormality or spontaneous abortion usually increases with age, and this risk increases after age 35. The annual increase in risk is much greater in the mid-to-late 30s than in the mid-20s, said Natalie Clark Stentz, medical director of the University of Michigan Health Center for Reproductive Medicine.
Data on fertility outcomes varies. According to the American College of Obstetricians and Gynecologists, for healthy couples between the ages of 20 and 30, the chance of a woman becoming pregnant in a single menstrual cycle is between 25 and 30%. By age 40, a woman’s chance of becoming pregnant is less than 10% per menstrual cycle.
Women are born with a set number of eggs, about one to two million, which die off as they age.
The American College of Obstetricians and Gynecologists states that a woman’s most fertile years are between her late teens and late twenties. When women reach their mid-thirties, they lose eggs more rapidly each year. At the age of 37, women still have around 25,000 eggs.
However, how quickly these eggs are used up varies from person to person. For example, chemicals in cigarette smoke can cause women to lose eggs. Metabolic disorders such as obesity and diabetes can also contribute to reduced reserves.
Researchers are increasingly studying the influence of genetics on egg reserves. For example, if a woman’s mother gives birth at age 40, that’s no guarantee that she’ll be able to get pregnant at that age, but it may increase the likelihood to some extent, Stentz said.
The quality of the eggs also influences fertility. As you age, the quality of the remaining eggs decreases.
As a woman ages, her ovaries gradually produce less estrogen and progesterone, making conception more difficult and eventually leading to menopause.
“Every decade, your cycles change,” said Mary Rosser, director of Comprehensive Women’s Health at Columbia University Irving Medical Center. “Hormones change, and that will also reduce your fertility.”
The older a woman gets, the more likely she is to develop a number of other medical conditions that can make pregnancy difficult. For example, fibroids (tumors in the uterus that can lead to infertility) are more common in women between the ages of 30 and 50.
As you age, your risk of developing diabetes, obesity and autoimmune diseases related to infertility also increases.
Researchers have paid much less attention to the question of how male fertility declines with age. But men also find it more difficult to get pregnant as they get older. Men produce new sperm throughout their lives, but as they reach age 40, their testosterone levels decline and they gradually produce poorer quality sperm. As we age, sperm may also change slightly in shape, making it difficult for them to swim quickly and fertilize eggs.
Like women, men are more likely to develop chronic diseases such as diabetes and high blood pressure as they age, which can make it difficult to conceive.
And scientists are learning more about behavioral factors that could 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 women over 35 who have tried unsuccessfully to conceive after six months have an infertility test.
Still, the number is a historical and practical indicator and not a biological limit, Rosser said. “I’m surprised 35 stayed like this,” he concluded.
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