Fertility naturally declines as females and males get older.
For instance, a female is born with all the eggs she will ever have naturally. Researchers currently believe that women are born with 1 million to 2 million eggs and that this number decreases throughout the lifespan. The decrease in fertility accelerates over time because of the reduction in the number and quality of eggs in the ovaries.1 The lower number of eggs leads to changes in hormone levels, which further reduces a woman's fertility. After a woman goes through menopause, there is no way for her to get pregnant naturally.
New research suggests that researchers may be able to create eggs from stem cells in the ovaries.2 The discovery of how to make eggs from stem cells could help women preserve their fertility or could remove age as a factor in infertility.
Increasing age also increases the risk for certain problems that can contribute to a loss of fertility.3 These include:
- Uterine fibroids
- Tubal disease, a general term that describes any number of infections that affect the fallopian tubes
- Genetic abnormalities of the remaining eggs, which can make them less viable or increase the likelihood that an infant will have conditions such as Down syndrome
In addition, lifestyle and environmental factors can combine with age-related factors to significantly decrease fertility.
In males, age is known to reduce the quality of sperm, which affects the sperm's ability to reach or fertilize an egg. Men also produce fewer sperm as they age.
Other age-related causes of reduced fertility in males include:
- Genetic abnormalities of the sperm, which can reduce the chances of their partner becoming pregnant or increase the likelihood of miscarriage or of an infant having a condition such as Down syndrome
- Erectile dysfunction, which can be affected by decreasing testosterone levels as a man ages or by medications for age-related conditions such as hypertension
- Changes to the reproductive tissues or organs. For example, testicle volume decreases with age. Also, men may have an enlarged prostate, which can cause problems with ejaculations.