Why does fertility decline as women age?

Women are born with all of the eggs they will ever have in their ovaries (unlike men who continue to produce sperm all their lives). They start out with more than a million eggs but only have about 300,000 left by the time they reach puberty, of which only about 300 are ovulated during the reproductive years. Also, as you age, both the quantity and quality of eggs are greatly reduced and the eggs that you ovulate are more likely to have genetic abnormalities.

The quantity and quality of your eggs — as well as how well the ovarian follicles are responding to hormonal signals from your brain — is referred to as the ovarian reserve, and it is an indicator of a woman’s fertility.

Many women don’t realize that their fertility begins to decline as early as their late 20s. A healthy 30-year-old woman has a 20 percent chance per month to get pregnant. A healthy 40-year-old woman has only a 5 percent chance of getting pregnant per month.

Fertility tests may include ovulation detection and evaluation of the fallopian tubes, cervix, and uterus.

A woman’s age is one of the most important factors affecting whether she is able to conceive and give birth to a healthy child. This is due to several changes:

•The number and quality of eggs (ovarian reserve) decreases naturally and progressively from the time a woman is born until the time she reaches menopause. This decline is gradual until her early 30s but accelerates quickly after her mid-30s.

• It is not only more difficult to get pregnant (conceive), but miscarriage and chromosomal abnormalities in the child (such as Down syndrome) are more common in older mothers.

• Fibroids, endometriosis, and tubal disease are more common and can affect fertility.

•Women who become pregnant at an older age have a higher risk of complications during the pregnancy, such as gestational diabetes and preeclampsia.

Anther factors can cause a decline in your fertility:

If you have any of the following risk factors, you may consider seeking advice earlier than described above:

-Family history (i.e., mother or sister) of early menopause (before age 51).

– History of cigarette smoking.

– Previous ovarian surgery.

-Exposure to chemotherapy or radiation to treat cancer.

– Shortening in the time between periods.

– Skipped or missed periods.

– Exposure to toxic chemicals (certain pesticides or solvents).

If a couple has an obvious medical problem affecting their ability to conceive, such as the absence of periods (amenorrhea) or irregular periods, sexual dysfunction, a history of pelvic disease, or prior surgery, they should begin the infertility evaluation immediately.