Age is one of the most important factors influencing fertility, particularly for women. While many people conceive naturally in their 30s and 40s, fertility gradually declines over time due to changes in egg quantity and quality. This guide explains how age affects both female and male fertility, what to expect at different ages, and when to seek a fertility evaluation.

How Age Affects Fertility: What You Should Know Before Trying to Conceive

Age is one of the most important factors affecting fertility, especially for women. While many people are able to conceive naturally in their 30s and even 40s, the chances of pregnancy gradually decline with age due to changes in both the number and quality of eggs. Male fertility also changes over time, although these effects are generally more gradual. Understanding how age influences fertility can help individuals and couples make informed decisions about family planning and know when to seek medical advice.

Why Does Age Affect Fertility?

Unlike men, women are born with all of the eggs they will ever have.

Before birth, the ovaries contain approximately 6 to 7 million eggs.

Over time, this number naturally declines:

Birth: 1 to 2 million eggs
Puberty: 300,000 to 500,000 eggs
Around age 37: Approximately 25,000 eggs
Around menopause: About 1,000 eggs

As women age:

The number of remaining eggs decreases.
Egg quality also declines.
Chromosomal abnormalities become more common.
Miscarriage becomes more likely.
It becomes harder to achieve pregnancy naturally.

Female Fertility by Age

Younger Than 30

These are generally considered the peak reproductive years.

Most women have:

The highest egg quality
The largest ovarian reserve
The lowest miscarriage risk
The highest monthly chance of pregnancy

Ages 30 to 34

Fertility remains relatively high but begins to decline gradually.

Most healthy couples still conceive naturally within one year.

Ages 35 to 39

Around age 35, fertility declines more noticeably.

Changes include:

Fewer remaining eggs
Lower egg quality
Increased miscarriage risk
Increased risk of chromosomal abnormalities

For women 35 years and older, fertility evaluation is recommended after 6 months of trying to conceive without success.

Age 40 and Older

After age 40:

Monthly pregnancy rates decline significantly.
Miscarriage rates increase substantially.
The likelihood of chromosomal abnormalities increases.
Fertility treatments may become less successful using a woman’s own eggs.

Natural pregnancy is still possible, but it becomes less likely with advancing age.

How Age Affects Egg Quality

Age affects not only the number of eggs but also their health.

As egg quality declines:

Fertilization becomes less likely.
Embryos are less likely to implant.
The risk of miscarriage increases.
The chance of chromosomal conditions, such as Down syndrome, increases.