Age and Female Fertility

Not all women are aware of the rate at which their fertility declines as they age.  Due to the prevalence of celebrities giving birth into their 40's, women are sometimes mistakenly led to believe that conception at that age is quite possible. What is most often not revealed is that the celebrity used a donated egg or embryo.

Women are born with all the eggs they will ever have. Of the 1,000,000 eggs baby girls have at birth, only 300,000 are left by the time she reaches puberty. Of that number, only about 300 eggs are ovulated during a woman's reproductive the rate of one egg per month.

Generally, women are most fertile in their 20's, then fertility begins to decline as they reach their late 20's. It is important to know that after age 35, the chances of a woman having a baby naturally decline by about 50%. After age 40, the changes decline by about 90%.

Before menopause approaches, a woman's reproductive capabilities slow down and become less effective at producing mature and healthy eggs. As a woman ages and comes closer to menopause, her ovaries no longer respond well to the hormones that are responsible for helping the ovulation.

For more details on age and fertility, review ASRM's guide for patients

The added risk of genetic problems


The age-related increased risk of miscarriage is caused, at least in part, by increases in chromosomal abnormalities. Most miscarriages occur in the first trimester for women of all ages. The risk of miscarriage increases with age. Studies suggest that the following miscarriage rate by age:

  • About 10% at ages 20 - 29
  • About 20% at ages 35 - 39
  • About 35% at ages 40 - 44
  • More than 50% by age 45

Down Syndrome

A woman's risk of having a baby with certain birth defects involving chromosomes (the structures in cells that contain genes) increases with age. Down Syndrome is the most common chromosomal birth defect. Affected children have varying degrees of mental retardation and physical birth defects. A woman's risk of having a baby with Down Syndrome is:

  • At age 25, 1 in 1,250
  • At age 30, 1 in 1,000
  • At age 35, 1 in 400
  • At age 40, 1 in 100

Experts recommend that all pregnant women, regardless of age, be offered a screening test for Down Syndrome and certain other chromosomal birth defects.

Multiple births

While women over age 35 may have more difficulty conceiving, they also have a greater chance of having twins. The chances of having twins increases naturally with age.

Options for family building

It is devastating for a woman to realize that she has age-related infertility. However, it is good to know that there are other ways to build a family. Some women may opt to adopt a child.  For those who would like to carry and give birth to a child, using an egg donor is a viable option. When using egg donation, it is the age of the egg donor, not the age of the recipient (or intended parent) that matters.