It’s a well-known fact as your age increases, fertility significantly diminishes over time. Aging is also associated with higher miscarriage rates. Unfortunately these changes are intrinsic to the egg, and today’s fertility technologies can’t alter the egg’s integrity.
The connection between age and fertility has been proved over and over again from data derived from earlier populations that didn’t use contraception. The evidence shows that the later a woman married, the fewer children she had, and as time went on, it was also less likely that she would have children at all. Age-related infertility is therefore not a problem of modern society. The issue with modern society is that a large percentage of women are waiting to marry and are delaying childbearing until their thirties and forties. This translates to a larger percentage of women who face fertility issues.
A classic French study in which women underwent insemination with donor sperm yielded 75% pregnancy rates for women under 31 after 12 months of insemination. For women ages 31-35, this figure decreased to 64%, and then again to 54% for women over 35. In IVF cycles, pregnancy rates markedly decline according to the age of the woman — for details about national IVF stats, check out this Clinic Summary Report.
Age is also associated with a corresponding decline in egg number and ovarian follicle count. Simply put, this means there are fewer eggs in the starting gate. Response to fertility medications is markedly different in women with a diminished ovarian reserve (which is the ability for the ovaries to provide eggs that can be fertilized and that will result in successful pregnancies). Age-related infertility describes the changes in quality of eggs with the aging female. Diminished ovarian reserve describes a decreased number of eggs. Unfortunately for women over the age of 38, these two factors frequently compound each other and can make it especially difficult for older women to become pregnant.
During treatments with fertility medications, providing women with extra hormones provides the necessary juice to fortify the smaller eggs in the race and allows them to continuing growing, reach maturity, and achieve ovulation. For women with diminished ovarian reserve, if the additional eggs are not in the starting corral at the onset of menses, extra drugs don’t yield additional eggs. Hence diminished ovarian reserve is associated with a poorer response to medication.
While pregnancy rates have been proved to decrease as a woman ages, miscarriage rates conversely have been shown to increase as the mother ages. Whereas a woman under the age of 35 has just a 15% chance of miscarriage, the rate increases to 20-35% from ages 35-45, and in women over 45, that rate leaps to 50%. (Source: http://americanpregnancy.org/pregnancycomplications/miscarriage.html.) So as we age, most women also have a decline in their egg quantity as well as egg quality. This makes the likelihood of having even one normal embryo much lower over time.
Additionally, there are several other factors that support the decline in reproductive rates in aging women including:
- An increased likelihood of endometriosis (a painful condition caused by the appearance of endometrial tissue outside of the uterus), adenomyosis (also painful with excessive bleeding; this is caused by endometrial tissue existing within and growing in the muscular wall of the uterus), or fibroids (benign tumors made of muscular and fibrous tissues in the pelvis).
- Since older women may have had more sexual encounters over time, there is potentially more exposure to sexually transmitted diseases or pelvic inflammatory diseases.
- Over a woman’s lifetime, an abnormal Pap smear may have been treated surgically with a resulting change in the cervical mucus.
- Older women are also more likely to have other illnesses related to infertility and/or health risk during pregnancy including thyroid dysfunction, hypertension, diabetes, and even a cancer diagnosis.
- Older couples also report fewer sexual encounters, which also may contribute to decreased fertility.
- New data supports the theory that there is a mild but real decrease in sperm quality with the age of the male partner, which may have a subtle effect on fecundity rates as well.
All of this is not meant to scare you, but to provide you with the knowledge to plan your life and make educated reproductive choices. Having a regular menstrual cycle is not synonymous with fertility, and although menopause may not occur until 51 or older, the ability to have a child beyond the age of 43 is rare. Egg donation has made the possibility of childbearing up to age 50 a reality for many women, but women of all ages need to understand the real facts of reproductive aging in order to make educated decisions and choices in their twenties and thirties.
If you have questions about age and fertility, talk to us!