Infertility affects about 1 in 6 adults worldwide, or 17.5% of the adult population, according to a 2023 World Health Organization report. Whether that number is truly rising in a biological sense is more complicated than it appears. Some measures of fertility are clearly worsening, particularly sperm counts in men. But shifts in when people try to have children, greater exposure to environmental chemicals, and changes in how infertility is tracked all contribute to a picture that looks different depending on where you focus.
What the Global Numbers Show
The WHO’s 2023 report analyzed studies from 1990 to 2021 and found that infertility rates are remarkably consistent across the globe. Lifetime prevalence was 17.8% in high-income countries and 16.5% in low- and middle-income countries. That similarity suggests infertility is not just a problem of wealthy nations with older parents or more pollution. It is a baseline human reality that affects every region.
In the United States, CDC data from 2015 to 2019 found that 13.4% of women aged 15 to 49 had impaired fecundity, meaning difficulty getting pregnant or carrying a pregnancy to term. That overall rate appeared unchanged from the previous survey period (2011 to 2015). However, among married women aged 15 to 44 who were actively trying to conceive, the infertility rate rose from 6.7% to 8.7% between those same periods. The distinction matters: the broader population rate held steady while the rate among those actually attempting pregnancy climbed.
Sperm Counts Are Falling Fast
The clearest biological signal that something is changing comes from male fertility. A landmark 2022 meta-analysis published in Human Reproduction Update examined sperm data collected globally from 1973 to 2018. Among men not selected for fertility status, average sperm concentration dropped by 51.6% over that 45-year window. Total sperm count fell even more steeply, declining 62.3%.
What alarmed researchers most was the acceleration. The annual rate of decline more than doubled after the year 2000, going from 1.16% per year to 2.64% per year. This is not a plateau or a slow drift. Sperm counts are falling faster now than they were a generation ago, and the trend shows no sign of leveling off. While low sperm count does not automatically mean a man cannot father children, it narrows the margin considerably and makes conception take longer or require medical help.
Why Parents Are Older Now
One of the most significant shifts driving infertility statistics is simply that people are trying to have children later. In 1990, women under 30 accounted for about 7 in 10 births in the United States. By 2023, that figure had dropped to fewer than 1 in 2. Meanwhile, births to women aged 35 to 39 increased 90%, and births to women 40 and older nearly tripled.
Fertility declines naturally with age, particularly after 35, when egg quality and quantity drop more sharply. This means a growing share of the population is attempting pregnancy during their least fertile years. Some of these parents successfully have children later. Others find that delaying means the window has closed. CDC researchers note that delayed childbearing produces a mix of “postponed and foregone fertility,” where some births simply shift to older ages while others never happen at all.
This demographic shift alone can make infertility appear to be rising even if the underlying biology at any given age hasn’t changed. When the average person trying to conceive is 33 instead of 25, more of them will struggle, and that shows up in the data.
Environmental Chemicals and Fertility
A growing body of evidence points to hormone-disrupting chemicals as a contributor to reproductive problems in both men and women. These substances, found in plastics, flame retardants, pesticides, and industrial processes, interfere with the body’s hormonal signaling. Some mimic natural hormones and trick receptors into activating. Others block hormones from reaching their targets. Either way, the result is disrupted reproductive function.
BPA, commonly found in plastics and food container linings, has been shown to compromise embryo implantation in women and alter the hormonal pathways central to reproduction. Phthalates, used to make plastics flexible, and flame retardants called PBDEs are also implicated. Lead, even at low levels, changes reproductive hormones in women and may shorten the overall window of fertility. DDT exposure early in life has been linked to earlier puberty, longer menstrual cycles, and earlier menopause in women.
There is also evidence that these chemicals alter germ cells, the precursors to sperm and eggs. This raises a troubling possibility: exposures in one generation could affect the fertility of the next. The challenge is that these chemicals are so pervasive in modern life that isolating their individual contributions is difficult, but cumulative exposure to dozens of them is now the norm rather than the exception.
Lifestyle Factors Affecting Male Fertility
Beyond environmental chemicals, several everyday habits are taking a measurable toll on sperm quality. Smoking reduces sperm concentration, motility, and the percentage of normally shaped sperm. In heavy smokers, structural damage to the sperm tail has been observed under microscopy. Electronic cigarettes are not a safe alternative: animal studies show they cause developmental defects in sperm and damage to the tissue that produces it.
Daily alcohol consumption reduces semen volume, sperm density, and motility. In men who drink heavily, the hormonal axis that controls testosterone production becomes disrupted, leading to lower testosterone levels and reduced fertilizing capacity.
Mobile phone use has also drawn scrutiny. The electromagnetic fields emitted by phones have been associated with increased oxidative stress in sperm and greater DNA fragmentation. One mechanism appears to involve heat: prolonged phone calls raise temperature in nearby tissues, which may affect the hormonal signaling chain that governs sperm production. Men who work with high-voltage equipment or in welding, which involves significant electromagnetic exposure, show worse sperm quality, and their partners face a higher risk of miscarriage.
Is It Real or Just Better Counting?
Part of the answer depends on what you mean by “rising.” The CDC has noted that infertility estimates vary significantly based on definitions, survey methods, and which population you study. Restricting your sample to women actively trying to conceive, for example, will yield a higher rate than surveying all women of reproductive age, because the group trying to conceive skews older and has been trying longer.
Societal trends in delayed marriage and childbearing also reshape who shows up in the data. When more people wait until their mid-30s to start trying, more people encounter age-related fertility decline, and more people seek medical evaluation. Greater awareness and reduced stigma around infertility mean more people are being diagnosed now than in previous decades, even if some of those cases would have existed undetected in the past.
That said, the sperm count data is hard to explain away through better counting. A 51.6% decline in sperm concentration over four decades, accelerating after 2000, points to something biological happening at the population level. The most likely explanation is a combination of factors acting together: chemical exposures building up across generations, lifestyle changes, rising obesity rates, and delayed parenthood all compounding one another. No single cause accounts for the trend, but the trend itself is real and, for sperm quality at least, getting worse.