Infertility does appear to be growing more common worldwide, though the picture is more complicated than a simple yes or no. Between 1990 and 2021, age-adjusted infertility rates increased by an average of 0.49% per year in men and 0.68% per year in women globally, according to the Global Burden of Disease Study. Several overlapping factors are driving this trend, from delayed childbearing to declining sperm counts to rising rates of conditions like polycystic ovary syndrome.
What the Global Numbers Show
As of 2021, roughly 55 million men and 110 million women worldwide were living with infertility. That works out to about 1.8% of reproductive-age men and 3.7% of reproductive-age women. In the United States specifically, about 13.4% of women ages 15 to 49 have what the CDC calls “impaired fecundity,” meaning difficulty getting pregnant or carrying a pregnancy to term.
These numbers have climbed steadily over the past three decades, even after adjusting for age. That adjustment matters because it means the increase isn’t simply explained by more people trying to have children later in life. Something beyond demographics is shifting.
Sperm Counts Are Dropping Fast
One of the most striking pieces of evidence comes from male fertility. A landmark meta-analysis covering samples collected globally between 1973 and 2018 found that average sperm concentration dropped by 51.6% among men in the general population. Total sperm count fell even more sharply, declining 62.3% over the same period.
Perhaps more concerning is the pace of that decline. The rate of decrease roughly doubled after the year 2000, accelerating from about 1.2% per year to 2.6% per year. Researchers don’t have a single explanation for this acceleration, but the pattern is consistent across continents, suggesting widespread environmental or lifestyle causes rather than something unique to one region.
People Are Having Children Later
The average age of a first-time mother in the United States is now 27.5, up significantly from previous decades. Fertility begins declining in the early 30s for women and drops more steeply after 35. For men, sperm quality also deteriorates with age, though less dramatically. When large numbers of people delay childbearing by even a few years, the population-level effect on conception rates is substantial.
Delayed parenthood is largely a response to economic pressures, longer educational paths, and shifting social norms. It’s a rational choice for many people, but it does mean that more couples encounter biological difficulty when they eventually try to conceive.
Rising Obesity Is a Major Factor
Excess weight affects fertility in both men and women through multiple pathways, primarily by disrupting reproductive hormones. Women with obesity face roughly 78% higher risk of infertility compared to women at a normal weight, and one prospective study found the risk was threefold higher in obese women than non-obese women. For every one-unit increase in BMI, the odds of conceiving spontaneously drop by about 10%.
Men aren’t spared. In a large study of over 26,000 planned pregnancies, overweight men had 20% higher odds of infertility at 12 months compared to normal-weight men, and obese men had 36% higher odds. Given that obesity rates have surged worldwide over the past 40 years, this alone could account for a meaningful share of the increase in infertility.
PCOS Is Becoming More Prevalent
Polycystic ovary syndrome, one of the most common causes of female infertility, has risen sharply. Global PCOS cases increased by roughly 56% in incidence and 59% in prevalence between 1990 and 2021. An estimated 11 to 13% of women worldwide now have the condition, and its prevalence has approximately doubled over the past three decades. Forecasts suggest the numbers will continue climbing through at least 2036.
Part of this increase reflects better awareness and broader diagnostic criteria. Three different sets of diagnostic guidelines exist, and the wider Rotterdam criteria (introduced in 2003) capture more cases than the original 1990 definition. But improved diagnosis doesn’t explain the entire increase. Rising obesity rates likely play a role, since excess weight worsens the hormonal imbalances that characterize PCOS and can push borderline cases into clinical territory.
Chemical Exposures and Reproductive Harm
A growing body of evidence links certain industrial chemicals to reproductive problems in both sexes. Chemicals known as endocrine disruptors can interfere with hormones at very low concentrations. The ones most studied in relation to fertility include phthalates (found in plastics, personal care products, and food packaging), bisphenol compounds, certain pesticides, and PFAS (the “forever chemicals” found in nonstick coatings and waterproof fabrics).
Phthalates are particularly well documented. Their breakdown products trigger oxidative stress in developing egg follicles, disrupting follicle growth and reducing estrogen production. Animal and human studies show that phthalate exposure lowers the number of healthy follicles available for ovulation. Prenatal exposure to phthalates has even been linked to reproductive problems in the next generation, including abnormal hormone levels and increased ovarian cysts in offspring.
These chemicals are now essentially ubiquitous in modern life. While no single study has definitively proven that environmental chemicals are responsible for population-level fertility declines, the biological mechanisms are well established, and exposure levels have increased dramatically since the mid-20th century, tracking alongside the drop in sperm counts.
More People Are Using Fertility Treatment
The rising demand for assisted reproduction offers indirect evidence that more people are struggling to conceive. In 2022, U.S. fertility clinics performed nearly 396,000 IVF cycles. That number has grown steadily year over year. For women under 35, live birth rates per egg retrieval are about 53.5%, dropping with age.
Greater use of fertility treatment reflects several things at once: more people experiencing difficulty, better access to clinics, reduced stigma around seeking help, and more people choosing to freeze eggs or embryos for future use. It’s not a pure signal of rising infertility, but the scale of growth is consistent with a population that’s finding it harder to conceive on its own.
Declining Birth Rates Are Not the Same Thing
It’s worth separating two things that often get confused: birth rates and infertility. Birth rates are falling in most countries, but that’s overwhelmingly driven by people choosing to have fewer children or no children at all, thanks to contraception, economic factors, and changing preferences. Infertility, by contrast, is a medical condition defined as the failure to conceive after 12 months of regular unprotected sex.
Demographers and clinicians measure these very differently. A country can have a plummeting birth rate while its biological infertility rate stays flat, simply because more people are using contraception or delaying parenthood by choice. The reverse is also possible. When you see headlines about fertility “crises,” check which definition is being used. The biological evidence does point to a real increase in infertility, but it’s a slower, more modest trend than the dramatic birth rate declines that dominate news coverage.