How Fertility Decreases with Age
It is no secret that women’s fertility declines with age. While 35 is widely publicized as the age at which a woman’s fertility will drop off a cliff, the truth isn’t so dramatic. Women do hit a fertility peak in their 20’s. Throughout their later 20’s and into their 30’s, it gradually wanes, with the risk of infertility increasing each year. Research shows that this gradual decline begins around the age of 27. Between 31 and 35 years of age, a woman’s chance of conceiving spontaneously without any intervention declines by roughly 3 percent annually. Once a woman passes the age of 35, that annual decline accelerates, and by 45, a woman has less than a 5 percent chance of becoming pregnant naturally.
Declines in Egg Quantity
Fertility decreases with age because the quality and quantity of a woman’s egg supply decreases. Women are born with a finite number of eggs within their ovaries. While men continuously produce sperm, women are born with all the eggs they will ever have. At birth, a woman will have anywhere between 1 million and 2 million eggs – but by 25, that number has dwindled down to somewhere around 300,000. That number continues to decrease exponentially until menopause. Even though a woman only ovulates once per month – typically around 400 times in a lifetime – each menstrual cycle, dozens of egg follicles are activated to prepare for mensuration. While just one egg typically is released, the other egg follicles are lost in this process.
Therefore, older women simply have fewer eggs, which can make conception more difficult. A woman between the ages of 19 and 26 with a partner of a similar age has about a 50 percent chance of conceiving during any one menstrual cycle. For women between the ages of 27 and 34, that number is about 40 percent, and for women older than 35, that number is 30 percent. All in all, it takes an older woman longer to get pregnant than a younger one.
Egg Quality Decreases
It is important to note that even if a woman in her 40s is still ovulating on a regular basis, the quality of eggs is likely to be significantly less than it would have been in her 20’s or 30’s. As a woman ages, the DNA inside of her eggs begins to degrade. The lower the egg quality, the lower her fertility. Abnormal eggs typically won’t fertilize or implant in the uterus. If they do, there is a significantly heightened risk of miscarriage.
Increases in Disorders That Impact Fertility
As women get older, they are at a higher risk of developing any number of disorders that can have a negative impact on fertility. For example, both endometriosis, a condition that causes the tubes to thicken with scar tissue, and fibroids are much more common in women over the age of 30, and both can cause fertility challenges. Obesity and diabetes can also have a negative impact on fertility, and they are also seen more commonly in older women.
Ultimately, fertility is very complex – and age is just one of the factors influencing it. To learn more about how age may be impacting your fertility, don’t hesitate to contact Rifaat Salem, MD for an appointment.