Infertility is far more common than most people realize. Around 17.5% of adults worldwide, roughly 1 in 6 people of reproductive age, will experience infertility at some point in their lifetime. If you’re struggling to conceive, you’re not facing something rare or unusual.
Global and U.S. Numbers
The 1-in-6 figure comes from the World Health Organization, which found surprisingly little variation across regions. Lifetime prevalence is 17.8% in high-income countries and 16.5% in low- and middle-income countries, making infertility a challenge that cuts across geography and economics.
In the United States specifically, about 13.4% of women ages 15 to 49 have what’s called “impaired fecundity,” meaning difficulty getting pregnant or carrying a pregnancy to term. Among married women actively trying to conceive, 8.5% meet the clinical definition of infertile. That number jumps to 19.4% for married women who have never had a child before. Even women who already have one or more children aren’t immune: 6% of them experience infertility when trying again.
What Counts as Infertility
The clinical definition has a specific timeline. For women under 35, infertility means not conceiving after 12 months of regular unprotected sex. For women 35 and older, that window shortens to six months because fertility declines more steeply at that point. Women over 40 are generally encouraged to seek evaluation sooner rather than waiting a set number of months.
These timelines exist because conception is a numbers game even for healthy couples. In your 20s and early 30s, the chance of getting pregnant in any single menstrual cycle is about 1 in 4. By age 40, that drops to roughly 1 in 10 per cycle. So even without a fertility problem, it can take several months, and longer doesn’t always signal something wrong. The cutoffs help distinguish normal variation from a pattern worth investigating.
Rates Are Gradually Rising
Infertility isn’t holding steady. Global data tracking prevalence from 1990 to 2021 shows a consistent upward trend, with rates increasing by an average of 0.49% per year for males and 0.68% per year for females. Researchers expect this climb to continue through at least 2040.
Part of the increase reflects better data collection and more people seeking diagnosis. But population growth, delayed childbearing, and changing health patterns are genuine contributors. Secondary infertility (difficulty conceiving after a previous pregnancy) is growing faster than primary infertility, and projections suggest it will account for about 83% of all infertility cases by 2050.
It’s Not Just a Women’s Issue
The male partner is the sole or contributing cause in roughly half of all infertility cases. Despite this, conversations about infertility still disproportionately focus on women, and men are less likely to be evaluated early in the process. When a couple is struggling to conceive, both partners benefit from testing.
Age Is the Biggest Factor, but Not the Only One
Fertility declines with age for both men and women, though the decline is sharper and more time-sensitive in women. A healthy woman in her early 30s has roughly a 25% chance of conceiving each cycle. By 40, that’s closer to 10%. The drop is driven primarily by a decline in egg quality and quantity, which accelerates in the mid-to-late 30s.
Lifestyle factors play a measurable role too. Smoking increases infertility risk by about 42% compared to never smoking, based on U.S. data from women ages 18 to 45. Cigarette smoke contains thousands of chemicals with known reproductive toxicity, affecting egg quality, hormone levels, and the uterine environment. Body weight matters as well: over 55% of women identified as infertile in one large analysis had a BMI of 30 or higher, compared to about 37% in the general population of the same age. Being significantly underweight can also disrupt ovulation.
Sexually transmitted infections are another preventable contributor. Untreated chlamydia and gonorrhea can cause scarring in the fallopian tubes, and the background rate of these infections varies by region, which partly explains why the causes of infertility look different in different countries even though the overall prevalence is similar.
Unexplained Infertility Is Common
Even after a full workup of both partners, about 30% of infertile couples receive a diagnosis of “unexplained infertility.” This means standard testing of ovulation, fallopian tubes, uterine structure, and sperm parameters all comes back normal, yet conception isn’t happening. It’s a frustrating diagnosis, but it doesn’t mean nothing can be done. Many couples with unexplained infertility respond to fertility treatments, and some conceive on their own with additional time.
Primary vs. Secondary Infertility
Primary infertility means you’ve never been able to conceive. Secondary infertility means you’ve had at least one pregnancy before but are now unable to conceive again. Secondary infertility is significantly more common and is growing faster globally. This surprises many people who assume that having one child means the next will come easily. Age, new health conditions, weight changes, or complications from a previous pregnancy can all shift the picture.
Among younger women (ages 15 to 19), secondary infertility already appears at a rate of about 1.9% per year, while primary infertility sits at 0.42%. Both rates shift across the reproductive lifespan, but the gap illustrates how much of the global infertility burden falls on people who have conceived before.