The Relationship Between Age and Fertility
A woman’s fertility naturally declines with age, especially after 20 years old. While women are born with all the eggs they’ll ever have, the quality and quantity of these eggs decrease over time. Each month after puberty, typically one egg ovulates, but many eggs undergo atresia, or natural degeneration, and die off.
Just as our energy levels diminish with age, so do the vitality and energy levels of the eggs. Fertility depends heavily on the energy needed for fertilization and the genetic integrity of the eggs during meiosis. This energy influences the embryo’s development and ability to implant into the uterine lining successfully.
The Impact of Delayed Childbearing
Recent trends show an increase in women delaying childbirth into their late 30s and 40s. This shift is reflected in statistics showing a 50% rise over the last two decades in women having their first child after age 35 in the United States.
As a woman ages, there are both decreased monthly fertility rates and an increased miscarriage rate. The dominant factor that causes age-related reduced fertility is the decline in egg quality. This decline is marked by an acceleration in follicular atresia, an increased rate of chromosomal abnormalities in resultant embryos, and decreased ovarian reserve. Age-related increased miscarriage rates are mainly due to an increased number of genetic abnormalities in resultant embryos.
A Look at the Numbers: Fertility Declines with Age:
- Age 30-35: Fertility declines approximately twofold compared to age 25.
- Age 40 and above: Involuntary infertility affects roughly 65% of women.
- If all fertility factors are perfect, the best anticipated monthly fertility rate in a woman without infertility is around 8% at age 38 and drops to 3-5% by age 40.
Factors Contributing to Age-Related Infertility
The main driver of reduced fertility with age is the decline in egg quality and quantity. This is characterized by:
- Increased follicular atresia
- Higher rates of chromosomal abnormalities in embryos
- Diminished ovarian reserve
Markers such as Follicle Stimulating Hormone (FSH), Anti-Müllerian Hormone (AMH), y Antral Follicle Counts (AFC) help assess ovarian reserve.
Fertility Treatment Options for Infertility or Reduced Fertility as a Result of Aging
Fertilización in vitro (FIV)
IVF is an option for women over 35 who are experiencing infertility, however, success rates depend on the number of viable eggs retrieved, fertilized, and transferred. This means that women with a poor response to stimulation or diminished ovarian reserve often see reduced pregnancy success.
Oocyte Donation
Women aged 43 years and older often proceed directly to oocyte donation to increase their chances of having a healthy child. Oocyte donation has become a viable option for those women whose infertility is age-related. Oocytes collected from superovulated egg donors are fertilized with sperm. The resulting embryos are then transferred to the recipient who has been treated with estrogen and progesterone to produce an endometrial environment suitable for implantation. Oocyte donation offers high success rates, even for women over 50, providing a viable path to parenthood despite age-related fertility challenges.
