Most women lose the ability to conceive naturally sometime in their mid-40s, though the biological endpoint is menopause, which occurs at an average age of 52 in the United States. The gap between those two numbers matters: fertility drops sharply years before periods actually stop, so the age when women stop having babies is almost always younger than the age when menstruation ends.
How Fertility Changes Decade by Decade
Women are born with about one million eggs. By puberty, roughly 300,000 remain, and the number keeps falling from there. Unlike sperm, which are produced continuously, eggs are a finite supply that declines in both quantity and quality over time.
At 30, a healthy woman has about a 20% chance of conceiving in any given menstrual cycle. That may sound low, but it adds up quickly over several months of trying. By 40, the per-cycle chance drops below 5%. By 45, natural conception is rare enough that reproductive medicine specialists consider donor eggs the only realistic path to pregnancy. The decline isn’t a cliff at any single birthday. It’s a steady slide that accelerates after 35 and becomes steep after 40.
Egg quality matters as much as egg count. As eggs age, they’re more likely to have chromosomal errors, which increases the chance of miscarriage and genetic conditions like Down syndrome. This is one reason pregnancy becomes harder with age even when ovulation still occurs.
Perimenopause: The Gray Zone
The transition to menopause, called perimenopause, typically begins in a woman’s 40s and can last anywhere from a few years to over a decade. During this time, the hormones that trigger ovulation become less consistent. Periods may come early, late, heavy, light, or skip months entirely.
Here’s the critical point: irregular periods do not mean infertility. If you’re still getting a period, even sporadically, your body is likely still ovulating at least some of the time. You haven’t reached menopause until you’ve gone a full 12 consecutive months without a period. Until that milestone, pregnancy remains possible. The oldest verified natural conception on record is a British woman who gave birth at age 59 after conceiving accidentally, well past her last expected period. That’s an extreme outlier, but it illustrates that ovulation can surprise you.
IVF Success Rates After 40
Assisted reproduction extends the window somewhat, but it can’t override egg quality. For women who start IVF at 40 or 41, the chance of having a baby after one cycle is about 13%, rising to 25% after three cycles. Those numbers drop fast with each passing year:
- Age 42 to 43: 6% after one cycle, 11% after three
- Age 44 and older: 2% after one cycle, 5% after three
Using eggs donated by a younger woman changes the equation entirely. A 45-year-old using donor eggs from a woman in her 20s has roughly the same success rate as that younger donor would. The uterus can carry a pregnancy well past the age when the ovaries stop producing viable eggs, which is why donor-egg pregnancies are possible into a woman’s 50s in some cases.
Pregnancy Risks Rise With Age
Getting pregnant is only part of the picture. Carrying a pregnancy safely also becomes harder over time. Compared to women in their 20s and early 30s, women 35 and older face higher rates of gestational diabetes, preeclampsia (dangerously high blood pressure during pregnancy), preterm birth, low birth weight, and cesarean delivery. A large analysis combining data from multiple studies found that age alone was an independent risk factor for these complications even after accounting for preexisting conditions like obesity and high blood pressure.
These risks don’t jump suddenly at 35. They increase on a continuum, with the sharpest rise happening after 40. Miscarriage rates also climb, driven largely by the higher rate of chromosomal abnormalities in older eggs. Most pregnancy complications become significantly more common past 40, which is why prenatal care for women in this age group often includes more frequent ultrasounds, earlier diabetes screening, and closer blood pressure monitoring.
The Typical Range
Menopause in the U.S. usually falls between ages 45 and 58, with 52 as the average. But natural fertility effectively ends several years before menopause for most women. A practical way to think about it: the vast majority of women can no longer conceive naturally by their mid-40s, even though their periods may continue for another decade.
There’s wide individual variation. Some women experience early menopause in their 30s or early 40s, while others remain fertile into their late 40s. Genetics plays a significant role. If your mother or older sisters went through menopause early, you’re more likely to as well. Smoking, certain medical treatments, and surgical removal of the ovaries can also end fertility earlier than expected.
For women planning ahead, the key takeaway is that the biological window for having children is narrower than the window for having periods. Fertility peaks in the 20s, remains reasonably strong through the early 30s, declines noticeably after 35, and becomes quite limited by 40 to 43, regardless of overall health.