A Woman’s best reproductive age is in her 20s. In the 30s the birth rate is gradually reduced, especially after 35 years, a healthy,fertile 30-year-old woman has a 20% chance of becoming pregnant every month that she tries. This means that for every 100 fertile women that are 30 years of age and are trying to become pregnant during 1 cycle, 20 of them will be successful, and the other 80 will have to try again. At the age of 40, the chance for a woman is less than 5% in one cycle, so that is less than 5 out of every 100 women that are expected to be successful every month.

Egg quality

Women are getting pregnant less and are having more miscarriages because the egg quality decreases as the number of remaining eggs reduces in number. These changes come out in the open once she reaches her mid to late 30s. Thus, the age of the woman is the most accurate test of the quality of the eggs. An important change in the quality of the eggs is the frequency of genetic abnormality called aneuploidy (too many or too few chromosomes in the egg cell). During fertilization, a normal egg must have 23 chromosomes, so that when it is fertilized by the sperm, which also has 23 chromosomes, the resulting embryo will have a normal total of 46 chromosomes. As a woman gets older, more and more of her eggs have either too few or too many chromosomes. This means that if fertilization occurs, the embryo will also have too many or too few chromosomes. Most people are familiar with the Down syndrome, a condition that results when the fetus has an extra 21 chromosomes . The majority of embryos with too many or too few chromosomes do not lead to pregnancy at all, or end up in miscarriage. This helps to explain the lower chance of pregnancy and a greater chance of miscarriage in older women.

EGG Quantity

Lowering of the amount of eggs containing follicles in the ovaries is called "loss of the ovarian reserve." Women begin to lose their ovarian reserve before they become infertile and, before they stop having regular periods.The women are born with all the follicles they will ever have, therefore the pool of awaiting follicles is gradually spent. The ovarian reserve is reduced, the follicles become less and less sensitive to FSH stimulation, so they require more stimulation for the eggs to mature and ovulate. First of all, the periods as a result can converge into short cycles, of 21 to 25 days apart. Eventually, the follicles are not able to respond sufficiently well to consistently ovulate,which leads to long, irregular cycles. Weakened ovarian reserve is usually age-related and happens because of the loss of the natural eggs and reduced average quality of the remaining eggs. However, young women, may have reduced ovarian reserve because of smoking, family history of premature menopause and due to an operation on the ovaries. Young women may have a reduced ovarian reserve, even due to unknown risk factors. There are medical tests for the ovarian reserve, but none of them have been proven to reliably predict the possibility of pregnancy. These tests do not determine whether a woman can get pregnant, but they may determine if the age-related changes of the ovaries have already begun. Women with poor ovarian reserve are less likely to conceive than women with normal ovarian reserve in the same age group. None of the tests or any combination of tests can be a 100% accurate. Test day of 3 FSH, antimüllerian hormone and estrogen levels include blood sampling at 2, 3, or 4-day of the menstrual cycle. High levels of FSH or estrogen show that there is a low ovarian reserve. However, many women with reduced ovarian reserve can have a normal level of FSH on day 3, so a normal day 3 FSH does not always confirm a normal ovarian reserve. Other tests of ovarian reserve, which are sometimes used include clomiphene citrate challenge test (CCCT) and ultrasound research of follicle numbers, called the quantity of antral follicles.

A woman's ability to conceive decreases the older she gets. If you are using your own egg cells, on average, the younger you are, the higher the chances of your success.

In 2010 (the year for which the most recent data is available), women which had in vitro fertilization (IVF) using fresh embryos created with their own fresh eggs, the percentage of cycles started, which led to live births (the national average) were:

  • 32,2% for women under the age of 35 years
  • 27,7% of women aged 35-37
  • 20,8% of women aged 38-39
  • 13,6% for women aged 40-42
  • 5,0% for women aged 43-44
  • 1,9% for women aged 45 years and older

Please note that IVF and intracytoplasmic sperm injection (ICSI) have had similar success, and, as such, are no longer presented separately. The above results are for IVF and ICSI together.

In the charts below, taken from the report ART Success Rates 2013 published by the CDC, Center for Disease Control and Prevention,a US government agency. This report has been generated from the national data from 467 hospitals and more than 190,000 IVF cycles.

The diagram above illustrates the infertility increase with the advancing age of the female.

  • Lowering of the success rates of live births due to female age begins at around age 30;
  • The curve becomes steeper (the number of eggs and egg quality decreases faster), beginning at about the age of 38;
  • At the age of 44 and above, the chance of bearing a child from IVF using a woman’s own eggs is close to none;
  • The success rate using eggs by women over the age of 44 is around 2% per attempt. Another point, shown here, is that when using donor eggs in IVF, the reduction in your success is not significant even considering the aging process ;
  • The age of the eggs is very important;
  • The age of the uterus, carrying the embryos does not matter.