It’s become a popular talking point among some of President-elect Trump’s most prominent supporters: America has an infertility problem.
“Why are so many couples infertile?” Robert F. Kennedy Jr., Mr. Trump’s nominee to lead the Department of Health and Human Services, asked in a September post on the social media site X. Dr. Casey Means, a former surgeon and health influencer who has advised Mr. Kennedy, has called infertility a “crisis.”
And Mr. Trump himself has said he would task Mr. Kennedy with investigating “the decades-long increase in chronic health problems,” including infertility, or the medical inability to conceive.
Like people in many other developed regions across the globe, Americans are having fewer children now than before — a demographic trend that has alarmed some conservatives in particular. Some of that is likely a result of social and economic factors, like steep child care costs, housing prices and more people choosing to forgo starting families.
But whether infertility is becoming more common is a different question, and a difficult one to answer conclusively. Still, researchers and doctors said they are worried about a few health trends unfolding in the United States that can affect fertility.
How scientists track fertility
Researchers use a few metrics to examine fertility and infertility, and each offers a slightly different picture of the current landscape in the United States.
Fertility rate: The Centers for Disease Control and Prevention measures the general fertility rate as the total number of live births in a year per 1,000 women between the ages of 15 and 44. In 2023, the most recent year of data available, the fertility rate in the United States was around 54 births per 1,000 women of reproductive age — what appears to be a historic low.
Another way researchers look at fertility is using the total fertility rate, which estimates the average number of children a woman is expected to have during her reproductive years. In 2023, the total fertility rate in the United States was a little over 1.6 births per woman, lower than the roughly two births per woman documented in 2001.
Birthrate: The C.D.C. calculates birthrate by dividing the number of live births over the course a year by the total population. In 2022, for example, there were 11 births for every 1,000 people. In 1995, that number was 14.8 per 1,000 people.
Like the fertility rate measures, this metric demonstrates that Americans are having fewer children.
But none of these statistics help differentiate between people who have decided not to have children and those who want to do so but are unable to conceive.
“The intention to become pregnant is extremely, extremely difficult to measure — it’s something we do not keep track of at a population level,” said Jorge E. Chavarro, a professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health who researches infertility.
Infertility: The C.D.C. tracks this by assessing the number of married women between the ages of 15 and 49 who report having had unprotected sex for at least a year without becoming pregnant. This metric excludes women who have been surgically sterilized.
Infertility rates have appeared relatively stable over the last several decades, with the latest data from 2015 to 2019 showing that 2.4 million married women of reproductive age were infertile. That data presents an incomplete picture, however. Not everyone who is trying to conceive is married, and not everyone with fertility issues is attempting to have a child in a given year.
Another key factor is called impaired fecundity, or difficulty in either getting pregnant or carrying a pregnancy to live birth. The C.D.C. has found that the percentage of women between the ages of 15 and 49 with impaired fecundity rose to 13.4 percent between 2015 and 2019, compared to around 10 percent of women between the ages of 15 to 44 reporting impaired fecundity in 1995.
Even with this incomplete picture of fertility, some researchers say they are monitoring a few health trends that could be affecting it.
People are having children later in life.
More people are choosing to have children later in life. In 2021, the average age at which U.S. women had their first child was 27.3, which the C.D.C. has said was a record high. And the number of American women over 40 who are giving birth has steadily increased over the last few decades.
With this shift comes an increased risk of fertility issues. Age is the factor that most influences fertility, doctors said. The older a couple is, the greater the chance they will struggle to conceive.
Female fertility starts to decline gradually around age 32, according to the American College of Obstetricians and Gynecologists, and then falls more significantly after age 37.
Male fertility tends to start declining around age 35, as men produce fewer sperm, and as their sperm become less viable.
Obesity rates are rising.
Obesity rates have steadily risen in the United States; a recent paper found that nearly three-quarters of adults in the country are now overweight or obese.
Obesity can impact ovulation in women, said Dr. Mary Rosser, the director of Integrated Women’s Health at Columbia University Irving Medical Center. Obesity is also closely connected to polycystic ovary syndrome, or PCOS, which causes women to ovulate irregularly, or in some cases not at all. Research suggests that between 70 and 80 percent of women with PCOS have infertility, and women with the condition are also more likely to miscarry.
Excess weight has also been linked to lower sperm quality in men.
Sexually transmitted infections have climbed.
Several sexually transmitted infections, including chlamydia and gonorrhea, can affect fertility. S.T.I.s have been on the rise in the United States for decades, although some have plateaued in recent years. The C.D.C. has pointed to a number of factors that drove rates up for years, including reduced condom use and closures of clinics that test for and treat the infections.
Chlamydia and gonorrhea, in particular, can both lead to pelvic inflammatory disease and damage the fallopian tubes if they go untreated, Dr. Rosser said. S.T.I.s often don’t cause symptoms, which means they are frequently not treated in time to stop them from affecting fertility.
Chemicals are cause for concern.
A wealth of research has found a link between reproductive health issues and exposure to harmful chemicals and substances found in personal care products, air pollution, plastics, pesticides and even food. Some of these compounds, like phthalates and bisphenol A, or BPA, are known as endocrine disrupters. This is because they can interfere with the function of our hormones, which are produced by the endocrine system.
Endocrine disrupters have been tied to infertility, both in women and in men, said Tracey Woodruff, director of the Program on Reproductive Health and the Environment at the University of California, San Francisco. Even very low levels of exposure to endocrine disrupters can increase the risks of reproductive health issues, she said. But scientists are not sure how this translates to an individual’s fertility.
“You’re not going to be able to remove an endocrine disrupter and then everybody gets pregnant,” said Dr. Vasiliki Moragianni, the medical director at the Johns Hopkins Fertility Center.
Researchers are also trying to understand whether some people might be particularly susceptible to endocrine disrupters at certain points in their lives, such as during puberty, said Genoa Warner, an assistant professor in the department of chemistry and environmental science at the New Jersey Institute of Technology.
Experts said more research is needed, given that most people are exposed to these substances every day, and that they are practically impossible to avoid.
