At age 40, your chance of conceiving naturally in any given menstrual cycle is roughly half what it was in your early 30s. About 50% of women who want to conceive at 40 will get pregnant naturally, but the timeline is longer, the miscarriage rate is higher, and the window for seeking help is shorter than it was even a few years earlier.
Per-Cycle and Per-Year Odds
In your late 20s and early 30s, the chance of conceiving in a single menstrual cycle sits around 20 to 25%. By 40, that number drops to roughly 10 to 15% per cycle. That doesn’t mean pregnancy won’t happen. It means each month is more like flipping a weighted coin, and you may need more months of trying before it lands in your favor.
Over the course of a year, about half of women trying to conceive at 40 will succeed naturally. That’s a meaningful number, but it also means the other half won’t, and fertility continues to decline month by month at this age. The American Society for Reproductive Medicine recommends that women over 40 seek evaluation sooner rather than later if pregnancy doesn’t happen quickly, rather than waiting the full 12 months that’s standard advice for younger women.
Why Fertility Drops at 40
The main driver is egg quality, not egg quantity (though both decline). By 40, a larger proportion of your remaining eggs carry chromosomal abnormalities. When a chromosomally abnormal egg is fertilized, it’s far less likely to implant successfully, and if it does implant, it’s more likely to end in miscarriage. Your ovaries also release eggs less predictably, and some cycles may not produce an egg at all.
Hormonal shifts play a role too. The signals between your brain and ovaries become less coordinated, which can shorten the second half of your cycle and reduce the time a fertilized egg has to implant in the uterine lining.
Miscarriage Risk at 40
Miscarriage is one of the biggest factors separating a positive pregnancy test from a baby in your arms. A large Norwegian registry study tracking hundreds of thousands of pregnancies found that women aged 40 to 44 had a miscarriage rate of about 32%, compared to roughly 10% for women in their late 20s. After 45, the rate climbed above 50%.
This means that even when conception succeeds at 40, roughly one in three pregnancies will end in loss, most often in the first trimester. The primary cause is chromosomal abnormalities in the embryo, the same egg-quality issue that makes conception harder in the first place. These losses are not caused by anything the mother did or didn’t do.
Chromosomal Condition Risks
Pregnancies that do continue past the first trimester carry a higher chance of certain chromosomal conditions. The risk of Down syndrome, for example, is about 1 in 100 at age 40, compared to 1 in 400 at 35 and 1 in 1,250 at 25. Screening tests available in the first trimester, including blood draws and ultrasounds, can assess this risk early in pregnancy with high accuracy. Diagnostic tests like amniocentesis can confirm results if screening suggests an elevated risk.
Pregnancy Complications to Expect
Women who conceive at 40 and beyond face higher rates of several pregnancy complications. Gestational diabetes occurs in about 14.5% of pregnancies in women 40 and older, compared to around 7% in women aged 25 to 35, roughly double the risk. Preeclampsia (dangerously high blood pressure during pregnancy), cesarean delivery, and preterm birth are also more common.
These risks don’t mean a healthy pregnancy at 40 is unusual. Most women in this age group who receive consistent prenatal care deliver healthy babies. But your care team will likely monitor you more closely, with additional blood sugar testing, more frequent blood pressure checks, and possibly extra ultrasounds in the third trimester.
What Fertility Treatment Can Offer
If natural conception doesn’t happen within a few months, fertility treatment can improve the odds, though success rates also decline with age. IVF success rates using your own eggs drop significantly after 40. Most clinics report live birth rates per IVF cycle of around 15 to 20% at age 40, falling to single digits by 43. Using donor eggs from a younger woman, however, brings success rates back up to 40 to 50% per cycle regardless of your age, because the egg quality is what matters most.
Fertility specialists can also run straightforward tests early on to check your ovarian reserve (how many eggs you have left) and whether your fallopian tubes are open. These results help determine whether natural conception is still a realistic path or whether treatment would save valuable time.
Factors That Work in Your Favor
Age is the single strongest predictor of fertility, but it’s not the only one. Women at 40 who are otherwise healthy, maintain a stable weight, don’t smoke, and have regular menstrual cycles tend to fall on the more favorable end of the statistics. Your partner’s sperm quality matters too. Male fertility declines more gradually, but sperm quality issues can compound the challenge, and a simple semen analysis can rule that out early.
Ovulation tracking with at-home test strips or basal body temperature charting can also help by narrowing your efforts to the most fertile days. At 40, timing matters more than it did at 30, because you have fewer high-quality eggs and potentially fewer ovulatory cycles per year.