Most women can conceive naturally into their early 40s, though fertility drops significantly after 35 and becomes very unlikely after 45. The hard biological ceiling is menopause, which typically occurs between ages 45 and 55. With assisted reproduction, particularly donor eggs, pregnancy is possible into the 50s, but the risks to both mother and baby rise substantially with age.
Natural Fertility by Age
Fertility doesn’t fall off a cliff at any single age, but it does follow a clear downward curve. In a large North American study tracking couples actively trying to conceive, about 79% of women aged 25 to 27 became pregnant within 12 months. For women aged 34 to 36, that number dropped to about 75%. For women 40 to 45, it fell to roughly 56%, though the range of uncertainty was wide, reflecting how much individual variation exists in that age group.
What drives this decline is the gradual loss of viable eggs. Women are born with all the eggs they’ll ever have, and both the number and quality decrease over time. A blood marker called AMH, which reflects remaining egg supply, tells the story clearly. The median level for women 30 to 35 is 2.55. By 40 to 45, it drops to 1.00. By 45 to 50, it’s 0.70, and nearly one in five women in that age range has already reached menopause.
Natural conception after 50 is extraordinarily rare but not impossible. The oldest verified natural conception is Dawn Brooke of Guernsey, who became pregnant at 59 in 1997. She initially thought her symptoms were cancer. A handful of other documented cases exist in the early to mid-50s, but these are true outliers. For practical purposes, natural conception after the mid-40s is unlikely for most women.
IVF With Your Own Eggs
IVF can help, but it can’t reverse the underlying biology of egg aging. For women 45 and older using their own eggs, the live birth rate per embryo transfer is about 4.4% at age 45 and drops to 0.8% at 46. In the largest single-center study of IVF in women 45 and older (over 1,000 cycles), there were zero live births in any woman aged 47, 48, or 49 using her own eggs.
Per cycle started (which accounts for cycles cancelled before a transfer could even happen), the live birth rate at 45 was 2.9%. That means roughly 97 out of 100 IVF cycles at that age don’t result in a baby. Most fertility clinics reflect this reality in their policies. UK guidelines, for example, recommend offering IVF up to age 42. Many clinics worldwide set similar cutoffs for treatment with a woman’s own eggs, not as arbitrary rules but because the success rates approach zero beyond that point.
Donor Eggs Change the Math
When the limiting factor is egg quality rather than the ability to carry a pregnancy, donor eggs from younger women dramatically improve the odds. Women over 45 using donor eggs have pregnancy rates of 30 to 35% and live birth rates of 20 to 25% per cycle. For women over 40 broadly, pregnancy rates with donor eggs range from 30 to 55%.
This is because the donor’s age, not the recipient’s, determines egg quality. The uterus itself remains capable of sustaining pregnancy well beyond the point when a woman’s own eggs are no longer viable. Registry data suggest that pregnancy outcomes with donor eggs remain relatively stable until about age 45, after which there’s a small but steady decline in success. Women in their late 40s and even early 50s have carried pregnancies to term using donor eggs, though the pregnancy itself carries elevated health risks at those ages.
Egg Freezing as a Bridge
Freezing your eggs at a younger age lets you preserve that earlier egg quality for later use. The timing matters considerably. Women who froze eggs before age 38 had a live birth rate of 38% when they later used them, compared to 29% for women who froze at 38 or older. Looking across multiple studies, 48% of women under 38 at freezing achieved a live birth or ongoing pregnancy, versus 21% of those 38 and older.
Both the European Society of Human Reproduction and the Nordic Fertility Society recommend freezing before age 35 for the best results. At that age, with 15 or more eggs frozen, the chance of eventually having a baby can reach up to 75%. Freezing eggs at 40 is still possible, but the payoff is substantially lower because the eggs themselves are already older.
Pregnancy Risks After 40
Getting pregnant is only part of the equation. Carrying a pregnancy safely becomes harder with age, regardless of how conception happened. In a study comparing women 40 and older to younger mothers, preeclampsia (dangerously high blood pressure during pregnancy) affected 4.6% of older mothers versus 1.5% of younger ones. Gestational diabetes occurred in 14.5% of women over 40, compared to 6.9% in the control group. That’s roughly triple the risk of preeclampsia and double the risk of gestational diabetes.
Rates of cesarean delivery, placenta problems, and preterm birth also increase. These risks don’t make pregnancy after 40 inadvisable, but they do mean closer monitoring and more careful management throughout.
Chromosomal Risks Rise Steeply
The risk of chromosomal abnormalities in the baby increases sharply with maternal age, particularly for Down syndrome. Compared to women in their 20s, the odds of Down syndrome are about 6 times higher for women aged 35 to 39, 22 times higher for women 40 to 44, and 34 times higher for women 45 and older. For other chromosomal conditions like trisomy 18, the increase is even steeper: 7 times higher at 35 to 39 and 33 times higher at 40 to 44.
Looking at all chromosomal abnormalities combined, the risk is about 5 times higher at 35 to 39, 16 times higher at 40 to 44, and 36 times higher at 45 and beyond, all relative to women in their 20s. A large Danish study of over 500,000 pregnancies confirmed these figures. Prenatal screening can detect most of these conditions early, giving parents information to make decisions, but the underlying biological risk increases with every year of maternal age.
The Practical Picture
The answer to “how late” depends heavily on what tools you’re willing to use and what level of risk you’re comfortable with. For natural conception, the practical window closes for most women somewhere in the early to mid-40s. IVF with your own eggs has diminishing returns past 42 and essentially no success past 46. Donor eggs extend the window into the late 40s and early 50s with reasonable success rates, though pregnancy complications become more common. A small number of women have conceived naturally in their 50s, but planning around that possibility would be like planning your retirement around winning the lottery.
If you’re in your 30s and thinking about future fertility, freezing eggs before 35 offers the strongest safety net. If you’re already in your 40s and want to conceive, time is the most important variable. Each year of delay at this stage has a much larger impact on your chances than it would have a decade earlier.