Roughly one person in six faces infertility at some point in life
Medically, infertility means no pregnancy after at least a year of regular unprotected sex. The World Health Organization reported in 2023 that about 17.5 percent of people experience it during their lives. Men alone explain twenty to thirty percent of cases, women twenty to thirty-five, and both partners twenty-five to forty.
The term only applies within the normal reproductive years, so it is not used for children before puberty or women after menopause. Counting cases is harder than it sounds, because organisations disagree on how long a couple must try before a diagnosis, and demographers sometimes simply measure childlessness among women of reproductive age. A delay of six to twelve months is often called subfertility, while failure after a full year is infertility, though people use the words loosely. A 1997 estimate put unresolved infertility at about five percent of couples worldwide; the WHO's 2023 figures give a lifetime rate near 17.5 percent and 12.6 percent at any given moment.
About 85 percent of infertile couples have a cause that can be found. On the female side hormones dominate: low oestrogen, disrupted GnRH signalling, polycystic ovary syndrome and ageing, which thins the store of eggs. Ovulation problems explain a quarter of identified cases, and seven in ten of those involve polycystic ovaries. Damaged fallopian tubes account for anywhere from 11 to 67 percent of female infertility depending on the population, endometriosis for 25 to 40 percent, and some women lose ovarian function before 40.
Male infertility usually comes down to poor semen, which is why semen quality serves as a stand-in for a man's fertility. Other causes include low testosterone, semen travelling backward into the bladder, failure to produce enough sperm, and blockages such as an obstructed vas deferens.
Timing matters on both sides. Conception is possible only in a window of up to seven days leading up to and including ovulation, with peak chances in the 24 hours after an egg is released, and cycle lengths vary widely. Fertility awareness methods track cervical mucus, body temperature or hormones to spot that window. Women are most fertile in young adulthood, less so after 35, and rarely conceive after 50; male fertility typically starts falling after 40.
Source: Infertility
