Yes, fertility decreases with age for both women and men, though the decline is steeper and starts earlier in women. The drop begins gradually around age 32, accelerates after 37, and by 45 natural conception is unlikely. Understanding the specific numbers at each stage can help you make informed decisions about family planning.
When Fertility Starts to Decline
For women, fertility doesn’t fall off a cliff at one magic number. It decreases gradually but significantly starting around age 32, then drops more rapidly after 37. In your 20s and early 30s, you have roughly a 1 in 4 chance of conceiving in any given menstrual cycle. By 40, that falls to about 1 in 10. By 45, getting pregnant naturally is unlikely for most women.
The age of 35 is often cited as a key threshold, and there’s a reason for that. It’s the age the American College of Obstetricians and Gynecologists uses to define “advanced maternal age,” based on evidence of declining fertility and rising risks for chromosomal abnormalities. That said, 35 is somewhat arbitrary. Some risks don’t meaningfully increase until 40 or later, and plenty of women conceive without difficulty in their late 30s. The decline is a slope, not a step.
What’s Happening to Your Eggs
Women are born with all the eggs they’ll ever have, roughly 2 million at birth. By puberty, that number has already dropped to about 400,000. At age 37, approximately 25,000 remain. By the average age of menopause (around 51), about 1,000 immature eggs are left, but they’re no longer fertile.
It’s not just the number of eggs that matters. Egg quality declines too. As eggs age, they’re more likely to have chromosomal errors during cell division. This is why older eggs are less likely to result in a viable pregnancy and more likely to result in miscarriage or genetic conditions like Down syndrome. The FASTER trial and the National Birth Defects Prevention Study both found a significant association between chromosomal abnormalities and births to women 35 and older.
Your body produces a hormone that reflects the size of your remaining egg supply. Levels of this hormone (called AMH, often measured during fertility testing) tend to peak in your early 20s and decline steadily from there. If you’re curious about your own egg reserve, a blood test can give you a snapshot, though it measures quantity rather than quality.
How Miscarriage Risk Changes
Age doesn’t just affect whether you can get pregnant. It also affects whether a pregnancy will last. A large population study published in The BMJ tracked miscarriage rates across age groups and found a striking pattern:
- Ages 20 to 24: roughly 9 to 11% risk of miscarriage
- Ages 25 to 29: about 12%
- Ages 30 to 34: about 15%
- Ages 35 to 39: about 25%
- Ages 40 to 44: about 51%
- Age 45 and older: over 90%
The jump between 35 and 40 is where the numbers become hard to ignore. At 40, roughly half of recognized pregnancies end in miscarriage, primarily because of the chromosomal errors that become more common in aging eggs.
Male Fertility Also Declines
Men produce new sperm throughout life, so their fertility doesn’t have the same hard biological limit. But that doesn’t mean it stays constant. Sperm quality drops with age: volume decreases, sperm move less effectively, and the percentage with normal shape falls. DNA damage in sperm also increases as men get older.
These changes tend to become noticeable after 40. Older fathers face longer time to conception with their partners and higher rates of miscarriage, even after accounting for the mother’s age. The risks of certain genetic conditions and developmental differences in offspring also rise with paternal age, though the overall numbers remain small for most men.
What IVF Can and Can’t Overcome
Assisted reproduction helps, but it doesn’t erase the age effect. IVF success rates using a woman’s own eggs show the same age-driven pattern. According to 2022 data from the Society for Assisted Reproductive Technology, live birth rates per egg retrieval are:
- Under 35: 53.5%
- Ages 35 to 37: 39.8%
- Ages 38 to 40: 25.6%
- Over 42: 4.5%
That last number is the one that surprises people. After 42, fewer than 1 in 20 egg retrievals results in a live birth. IVF can’t fix egg quality, and egg quality is the main issue driving age-related decline. Using donor eggs from a younger woman largely eliminates the age penalty, which is why donor-egg IVF success rates remain high regardless of the recipient’s age.
Egg freezing works on the same principle. Eggs frozen at 30 retain the fertility potential of a 30-year-old, even if they’re used a decade later. The earlier eggs are frozen, the better the odds they’ll lead to a successful pregnancy down the road.
Timelines for Seeking Help
Medical guidelines use age to determine how long you should try before getting evaluated. If you’re under 35, the standard recommendation is to try for 12 months of unprotected intercourse before seeking a fertility workup. If you’re over 35, that window shortens to 6 months. For women over 40, more immediate evaluation is warranted because the window for effective treatment narrows quickly.
About 15% of couples experience infertility, and age is only one of many factors. Conditions like endometriosis, polycystic ovary syndrome, blocked fallopian tubes, and low sperm count all affect fertility independently of age. A younger person with one of these conditions may have more difficulty conceiving than an older person without them. Age sets the biological backdrop, but it’s not the whole picture.