In life achievements, age may be just a number. But with fertility, that number matters. In fact, a woman’s age is the most significant factor when it comes to fertility. 

Starting as early as your mid-30s, your ability to conceive and have a healthy baby is on the decline. Your biological clock, as it relates to fertility, is real. Why? Because as you grow older, your ovaries and the eggs inside of them age, too. 

Women are born with all the eggs they’ll ever have—1 to 2 million, according to the American College of Obstetricians and Gynecologists (ACOG). With the arrival of your first period, it's estimated that you'll have between 300,000 to 500,000 eggs left. By age 37, that number drops to 25,000, and typically will be down to 1,000 by the time you reach menopause.

Your age also affects the quality of your eggs. As birthdays go up, egg quality goes down. An egg is considered of lower quality when it has chromosomal abnormalities, making it less likely to be fertilized successfully. If fertilization does happen with a lower-quality egg, it can compromise the development of the embryo, increasing the chance of miscarriage or developmental issues.

Physiologically, there is a clear advantage to having kids at a younger age: Getting pregnant is easier, and the risks during pregnancy are lower. But for many people, this isn't feasible. So what does the ability to conceive look like as the years go by? Here is an overview of fertility in your 20s, 30s, and 40s. 

Your 20s: Prime Time for Conception

If fertility were a mountain, your fertility rate would hit the summit from 18 to 24. That’s because this is when you have the highest number of quality eggs. 

Between 25 and 29, you are still at a peak. Research indicates that women in their 20s to early 30s have a 25% to 30% likelihood of conceiving during a single menstrual cycle. 

Other good news: The risk of miscarriage is low at this stage. In a study published in BMJ that assessed 421,000 pregnancies, women between 25 and 29 had the lowest miscarriage rate, at 10%

Most healthy couples trying to conceive at this stage will be pregnant within 12 months. If you have been trying unsuccessfully for a year, consider speaking with your physician about an infertility evaluation.

Your 30s: Navigating Fertility Changes and Challenges 

To crib a phrase from The Hunger Games, the odds are still ever in your favor in your early 30s. But in your late 30s, your fertility will generally have begun a steady decline. 

According to a study conducted by the National Survey of Family Growth, the infertility rate in women ages 15 to 34 ranged from 7.3% to 9.1%. But in women 35 to 39, that rate jumped to 25%. In other words, with egg quality and quantity on the downslope, it might take longer to conceive in your late 30s.

Women 35 or older are considered to be at “advanced maternal age.” It may sound like an insult, but it’s simply a medical classification used mainly by the insurance companies to cover testing for conditions that could result from health challenges or age, including:

• gestational diabetes
• preeclampsia
• premature birth
• low birth weight
• miscarriage
• chromosomal conditions (such as Down syndrome)

If you are 35 or older and have been trying to conceive for six months, we recommend speaking with your ob/gyn for a fertility evaluation. The sooner you figure out what’s going on, the sooner you may find treatments.

Your 40s: Weighing Increased Risk and Fertility Options

It’s no secret that older women have a harder time getting pregnant. Specifically, by the age of 40, the chance of conceiving drops to 10% for each menstrual cycle, and with pregnancy, the risks of miscarriage and complications rise dramatically.

You probably know someone (or a celebrity) who’s had a baby in their 40s. It certainly isn’t out of the question. In fact, the Centers for Disease Control and Prevention reports a consistent increase in the number of women in the United States conceiving after the age of 40. Since 1985, there’s been an upward trajectory every year. In 2022, for example, there were 12.5 births per 1,000 women ages 40-44, reflecting a 4% rise compared to the previous year.

When you reach 45, conceiving  spontaneously is difficult, if not unlikely. And the risk for miscarriage jumps to 53%. At this point, many people look to advanced reproductive assistance, including the use of donor eggs, as a more viable solution for conceiving.

If you are 40 or over, it’s a good idea to chat with your physician before trying to get pregnant. Their guidance is essential if you have any health conditions that might cause issues. It’s important to understand the potential risks and alternative approaches for a healthy pregnancy.

While age is a key factor in your fertility, overall health plays a strong supporting role. Eating a balanced diet, getting enough exercising, and avoiding alcohol and smoking can boost your odds for a healthy pregnancy.