By nature, women face more difficulties with fertility after 40. Studies show that fertility begins to decline after age 30. It drops even more around age 37 and then fertility after 40 sharply declines.
The pregnancy success rate for a 40-year-old woman is only about 5 percent each month and on average, only 36 percent of woman over age 40 will get pregnant on their own. Due to the difficulties that women encounter with fertility over 40, fertility testing for women in their 40s is recommended as soon as they decide to try to get pregnant.
What are the main reasons for the decline in fertility after 40?
A key reason why women have barriers to fertility after 40 is that as women age, so do the eggs in her ovaries. These aged eggs are more likely to have genetic abnormalities.
Eggs are created by cell division and as the woman gets older, there is a greater chance for mistakes to occur in the division process. Those mistakes can cause an abnormal number of chromosomes in the egg.
Due to the higher number of eggs with abnormal chromosomes that a 40-year-old possesses, the complications of these genetic abnormalities are threefold for the woman trying to increase fertility after 40.
First, a child born with a chromosomal abnormality can suffer from birth defects and severe medical conditions. The most well-known of these is Down syndrome. A child born to a 40-year-old mother has a 1/66 chance of having a chromosomal abnormality. The chances increase with each year after that. In comparison, a 30-year-old mother has a 1/385 chance of having a child with genetic abnormalities.
Next, if one of the eggs with abnormal chromosomes gets fertilized, it will most likely end in miscarriage. Half of all miscarriages are due to abnormal chromosomes. Women aged 40-44 who do get pregnant have a 34 percent chance of miscarriage.
Lastly, such severe chromosomal abnormalities of the embryo can develop that implantation cannot even occur. This can help explain why older women have such a difficult time conceiving.
Another reason for infertility after 40 is due to an older woman’s ovarian reserve. A woman’s fertility potential is determined by her ovarian reserve, assuming no other reproductive problems exist.
You see, women are born with all the eggs they will ever produce and that number decreases by the hundreds every month. Her ovarian reserve depends not only the quantity but also the quality of the eggs in her ovaries, as well as the quality of the response of ovarian follicles to hormone signals from the brain. As women age, a natural loss of eggs occurs as well as a decrease in the quality of those eggs.
In the few years preceding menopause, the body produces more FSH and LH due to a decrease in response of the ovaries to these hormones. Menstrual cycles become shorter and eventually stop altogether. The average age of menopause is 50 and by then, ovaries stop functioning and there are few or no eggs left.
Other factors can also cause a decrease in the lifespan of the ovaries, making fertility after 40 difficult. Such factors include smoking cigarettes, chemotherapy or radiation from cancer treatment and diseases of the ovaries.
What types of tests are used to determine a woman’s ovarian reserve?
Doctors can perform numerous blood and imaging tests to try to determine ovarian reserve. These tests are performed on specific days of the menstrual cycle and include blood tests to determine levels of FSH, E2, Inhibin B, or AMH. An ultrasound can also be performed to measure the ovary size and number of antral follicles.
Fertility treatment options
Once a decreased ovarian reserve has been established there is no medical intervention that can reverse the damage. However, doctors will typically try to stimulate the ovaries using high doses of gonadotropins (LH and FSH). Generally, that treatment is also used in conjunction with giving the woman various other medications such as oral contraceptives, Lupron, clomiphene or Antagon.
If ovarian response does not improve after those treatments, the woman can choose to use donor eggs in the hopes of achieving a successful pregnancy. Egg donation accounts for approximately 10 percent of all Assisted Reproductive Technology (ART) and has about a 40 percent live birth rate per transfer. The recipient’s age, even if over 40, does not affect the birth rate when using donor eggs.
If egg donation is pursued as fertility treatment for women over 40, both the recipient and the donor will undergo thorough evaluation to ensure optimal results. Recipients are given dosages of estrogen and progesterone before, during and after the procedure in order to provide the optimal environment for an embryo.
Egg donation poses minimal risks to the recipient; the principal risk being multiple pregnancies due to the number of embryos transferred. The likelihood of making a healthy baby through this option is much greater as the risks of miscarriage and Down syndrome are greatly reduced.
Lastly, it is important to note that pregnancy can be much more difficult on women over 40. These women are at greater risk for complications such as hypertension, gestational diabetes, miscarriage, ectopic pregnancy, placental problems or cesarean delivery.
Sources: American Society for Reproductive Medicine: Age and Fertility. A Guide for Patients. IntegraMed: Can We Wait to Get Pregnant? IntegraMed: Fertility over 40- Age-Related Infertility Female Infertility: Tests and Diagnosis Resolve: The Medical Aspects of Egg Donation MarchofDimes.com: Pregnancy after 35
