Pick flowers when they are in bloom, don’t wait until there are no flowers left to pluck – cherish the fertility window

Author: Zou Yaoyu Shanghai Ji'ai Genetics and Infertility Diagnosis and Treatment Center, Obstetrics and Gynecology Hospital, Fudan University

Reviewer: Fu Jing, Chief Physician, Shanghai Ji'ai Genetics and Infertility Diagnosis and Treatment Center, Obstetrics and Gynecology Hospital, Fudan University

Age is the most important factor affecting fertility. With the increasing pressure of modern life and the decline of people's desire to have children, some people choose to be single or keep contraception during their childbearing years, but when they want to have a baby, they can't get pregnant, or they have problems with their babies after several prenatal examinations. So when the "flower" of fertility is ready to be broken, you should break it decisively, and don't wait until there is no "flower" of fertility left with regrets.

Generally speaking, the best childbearing age for women is 22 to 28 years old. During this period, women's bodies are fully developed, their eggs are of the best quality, there are fewer complications, and the incidence of embryo malformations after pregnancy is low. 29 to 35 years old is a plateau period, and the decline in fertility is not obvious. However, after the age of 35, ovarian function will plummet. At this time, not only will it become difficult for women to get pregnant, but the quality of eggs will also drop sharply, greatly increasing the probability of fetal malformations. Women over 35 years old are considered advanced women. The probability of a healthy 30-year-old woman getting pregnant is 20%, and by the age of 40, the probability of getting pregnant is as low as 5%. After menopause, they completely lose their fertility.

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In recent years, assisted reproductive technology has become well known to people. A considerable number of people think that there is no need to rush to get pregnant when they are young, as there is "test tube baby" to cover the bottom line. But is test tube baby really a tried and tested fertility insurance? Here we must realize that the success rate of test tubes for women drops sharply after the age of 40. It can be said that 40 years old is the "key to female fertility". According to a US report based on more than 120,000 assisted reproductive technologies, the test tube success rate for women under 35 years old can reach 43.2%, the success rate for women aged 38 to 40 is 30% to 40%, and the success rate for women aged 41 to 42 is 15.1%, and the success rate for those over 42 years old is only 5.9%. Therefore, once you cross the threshold of 40 years old, it is difficult to successfully give birth to a baby even with the help of "external forces".

Although neuroendocrine and uterine factors also affect fertility, changes in ovarian physiological function are the most important factor in reproductive aging.

1. Age and number of eggs

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Unlike men who can produce sperm throughout their lives, women have the most eggs at birth, with about 1 million to 2 million primordial follicles, each containing an immature egg. Most follicles degenerate during childhood. A woman's first menstruation is called menarche, which usually occurs between the ages of 12 and 14, with an average age of 13. At this time, there are 300,000 to 500,000 egg cells left. After that, among the 1,000 or so eggs that decrease each month, only one matures and provides a chance for conception. In addition to this mature egg, the other "companion" eggs will undergo cell apoptosis. Girls' ovulation in early adolescence is often very irregular, their menstrual cycles are disordered, and the amount of menstruation is more or less, but after the age of 16, ovulation and menstrual cycles will become regular, the reproductive system becomes more and more mature, and women's menstrual cycles will remain regular thereafter. During the reproductive period, women will discharge about 400 to 500 eggs in their lifetime. Until the period from the 30s to the early 40s, the menstrual cycle will become shorter. As the reserve of oocytes in the ovaries decreases, women begin to experience anovulation, fewer and fewer menstrual periods, until menopause stops completely. The average age of menopause for women in my country is 51 years old.

2. Age and egg quality

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Age has a significant impact on egg quality. With age, the probability of chromosomal abnormalities increases significantly. This is because the egg is prone to chromosome segregation errors during meiosis, and the ability of older women to repair chromosomes decreases, resulting in more chromosomal abnormalities in the embryo, thereby increasing the risk of miscarriage and fetal malformations. At the same time, the mitochondria of the egg are the main source of cellular energy. With age, mitochondrial function will gradually decline, resulting in insufficient energy supply, affecting the development and maturation of the egg. In recent years, more and more studies have found that with age, the body's antioxidant capacity decreases, and the level of reactive oxygen increases, leading to cell damage and apoptosis. Oxidative stress has a particularly significant effect on the egg, which can damage the DNA and other cell structures of the egg and affect the quality of the egg. In addition, the follicular cells and microenvironment around the egg will also change with age, and the function of the follicular cells will decline, affecting the nutrient supply and signal transmission of the egg, and then affecting the maturation and quality of the egg. These factors work together to reduce the quality of the eggs of older women, affecting fertility and embryonic development potential. This is why older women face higher risks during pregnancy, such as infertility, miscarriage, and fetal chromosomal abnormalities.

In addition, older women are more likely to have acquired diseases such as uterine problems, hormonal changes, endometriosis, uterine fibroids and pelvic infections, which can also affect the reproductive function of the ovaries.