Age is the most important factor in fertility, influencing various aspects of reproductive health. Here you will learn in less than 2 min how age affects fertility, covering oocyte quality, hormonal changes, and uterine readiness.

Oocyte Quality and Quantity

A woman's fertility starts to decline in her late 20s and early 30s, with a steeper decline after age 35. This decline is due to the reduction in both the quantity and quality of oocytes. According to the American Society for Reproductive Medicine (ASRM), a woman is born with approximately 1-2 million eggs, but by puberty, this number decreases to about 300,000-400,000. Each menstrual cycle, a woman loses about 1,000 eggs, and by age 37, only about 25,000 remain. By age 40, fewer than 10,000 eggs are typically left.

The quality of oocytes also diminishes with age. Studies show that the incidence of chromosomal abnormalities in eggs increases as women age, leading to higher rates of miscarriage. A study published in *Human Reproduction* indicated that the rate of chromosomal abnormalities in embryos increases from around 30% in women under 35 to over 60% in women over 40.

Hormonal Changes

Age-related changes in hormone levels significantly impact fertility. As women age, the levels of key reproductive hormones such as estrogen, progesterone.

The decline in estrogen and progesterone affects the menstrual cycle, leading to irregularities and anovulatory cycles (cycles where no egg is released). These hormonal changes make it more challenging to conceive naturally and maintain a pregnancy.

Usually this happens more after 45 years old.

Uterine Readiness

The ability of the uterus to support a pregnancy will also decline with age. The endometrium, the lining of the uterus where the embryo implants, may become less receptive. Conditions such as fibroids, endometriosis, and uterine polyps are more common in older women and can interfere with implantation and pregnancy maintenance.

A study published in *Fertility and Sterility* found that endometrial receptivity declines with age, which can affect the success rates of both natural conception and assisted reproductive technologies (ART). This decline is partly due to changes in the expression of genes involved in implantation and the inflammatory environment of the uterus.

Assisted Reproductive Technologies (ART)

For those facing age-related fertility challenges, ART can be a  solution. However, success rates of ART, including in vitro fertilization (IVF), also decline with age. According to data from the Society for Assisted Reproductive Technology (SART), the success rate of IVF for women under 35 is around 41%, but this rate drops to about 12% for women aged 41-42.

Many women over 40 consider using donor eggs, which can significantly increase the chances of successful pregnancy. Studies have shown that the use of donor eggs can result in live birth rates comparable to those of younger women, as the quality of the egg is a primary factor in successful implantation and development.

Lifestyle Factors

Lifestyle choices can exacerbate the natural decline in fertility with age. Smoking, excessive alcohol consumption, poor diet, and lack of exercise can negatively impact reproductive health. Smoking, for instance, accelerates the loss of oocytes and can lead to earlier onset of menopause. A study in the *British Medical Journal* found that women who smoke experience menopause about 1-4 years earlier than non-smokers.

Maintaining a healthy lifestyle, including a balanced diet, regular exercise, and avoiding harmful substances, can mitigate some age-related fertility declines. Additionally, stress management and maintaining a healthy weight are crucial for reproductive health.

Conclusion

Understanding the impact of age on fertility is essential for making informed reproductive choices. While age-related declines in fertility are natural, being aware of the factors involved and taking proactive measures, including lifestyle changes and considering ART, can help manage and potentially extend fertility.