How does a Woman's Fertility Change with Age?

It is medically proven that the best time for a woman to bear children is between the ages of 20 and 35. By the age of 20, most women have reached full physiological and sexual maturity, and after 35, their fertility decreases and the physical problems associated with being an older mother increase rapidly. Within this age bracket is an optimum age for a woman to become pregnant. Many authorities would agree that this is between the ages of 22 to 26. Fertility generally tends to decline after the age of 30.

Women are born with a certain number of eggs, which were created when they were still a fetus.  The number of eggs diminishes as women use up one or more eggs during their monthly (or thereabouts) ovulation. Also, due to the long incubation period of these eggs (they have been present since fetal development), they lose their quality as a woman gets older. A typical 30-year-old woman has 12% of the ovarian reserve she was born with, and has only 3% of ovarian reserve at age 40.

It has become increasingly common for many women to postpone pregnancy due to financial, vocational or relationship-related constraints. This has created a rise in woman wanting to get pregnant in their 30s and 40s, when they are less able to conceive. Consequently, infertility appears to be on the increase.

As a female gets older, her ability to conceive is reduced greatly because of the reasons stated above. The following statistics of women trying to get pregnant without using fertility drugs or in vitro fertilization support this notion:

• At 30-years-old, about 75% will get pregnant within one year, and 91% within four years.

• At 35-years-old, about 66% will get pregnant within one year, and 84% within four years.

• At 40-years-old, about 44% will get pregnant within one year, and 64% within four years.

Other claims on female infertility differ slightly in numbers. However, they continue to support the notion that a woman's fertility decreases as she gets older:

• At 35-years-old, about 94 out of every 100 who have regular unprotected sexual intercourse will get pregnant after 3 years of trying. 

• At 38-years-old, about 77 out of every 100 will get pregnant after 3 years of trying.

The above figures are for pregnancies ending in a live birth.

• About 9% of recognized pregnancies for women aged 20 to 24 end in miscarriage.

• About 20% at age 35 to 39 end in miscarriage.

• More than 50% by age 42 end in miscarriage.

So not only does a woman's chance of conceiving decrease with age, but so does her ability to carry a pregnancy full-term.

The use of fertility drugs and/or in vitro fertilization can increase the chances of becoming pregnant at a later age. Successful pregnancies facilitated by fertility treatment have been documented in women as old as 67. This does lead to certain ethical questions.

Doctors recommend that women over 30 who have been unsuccessful in trying to conceive for more than six months undergo some kind of fertility testing, as they fall into the age where fertility decreases.  Ascertaining the reason as to why the woman hasn't conceived is conducive to the commencement or continued progress of their treatment.