The Correlation of Aging and Fertility
Statistics support the belief that fertility decreases with age. Women over the age of 35 (compared to younger women) seek evaluation for infertility twice as many times. Some investigators have suggested that this decline is caused by the decreased frequency of intercourse in “mature couples”. For this reason, investigators in France studied the fertility rate amongst women who were attempting to become pregnant via a donor insemination program. This way, the frequency of intercourse did not interfere with calculations of fertility. As predicted, the fertility rate dropped significantly after the age of 30 and again after the age of 35.
AGING AND FERTILITY
The Correlation of Aging and Fertility
Increased possibility of Miscarriage with age
In addition to the lower chances of conception, as women age their likelihood of having a miscarriage increases. The longer an egg sits around in the ovary, the more likely it is to develop abnormalities in its chromosomes too. If an egg with abnormal chromosomes is fertilised, the greater the chances of a miscarriage.
The single most common cause of miscarriage is due to chromosomal abnormality. From the many studies conducted, least 2/3 of all miscarriages are caused by abnormal chromosomes. Therefore, a young women (in her 20s), has only a 12-15% chance of having a miscarriage each time she becomes pregnant while a women in her 40s has a 50% risk of miscarriage.
Down’s Syndrome and other Chromosomal problems
However, not every pregnancy in which the embryo has abnormal chromosomes will end in a miscarriage. Some embryos may develop and can result in the birth of a live baby. However, these babies can have varying problems such as birth defects and mental retardation with the most common problem being Down’s syndrome is the most common problem of this type but there are others.
Why does Fertility Decrease?
Women in their forties, fifties, and even sixties can still achieve very high pregnancy rates with egg donation while women who attempt IVF with their own eggs see a steady decline the chances for a live birth. Therefore, we can conclude that age impacts fertility caused by aging of the eggs and chromosomes. Studies that have removed eggs from the ovaries of older women have shown that a large percentage of cells have abnormal chromosomes.
AMH and Ovarian Reserve
Anti-mullerian hormone (AMH) is a hormone produced by the viable follicles (which contain eggs) that remain in the ovary. It is an excellent indicator of ovarian reserve. Young women with large numbers of healthy eggs tend to have higher AMH levels compared to older women or women with a low number of healthy eggs.
AMH levels do not fluctuate very much and are not impacted by the levels of other hormones including estrogen or progesterone. Abnormal AMH levels can be determined by comparing an individual’s AMH level with that of a larger group of women of her own age who are not infertile. Take for instance, an AMH of 1.4 would be considered very low for an 18-year-old but would be considered average for a 36-year-old.
FSH (Follicle Stimulating Hormone) and Ovarian Reserve
The Follicle Stimulating Hormone (FSH) is made in a gland near the brain gland called the pituitary. It is the hormone responsible for the cyclic development of eggs every month. As a woman’s eggs become less fertile, the levels of FSH begin to rise. Therefore, FSH usually increases in women as they age. Women who have gone through menopause tend to have very high levels of FSH. However, young women may also have high FSH levels when there is an accelerated decline in the quantity or quality of their eggs.
Fertility decreases with age due to aging eggs and the chromosomes inside them. Therefore. resulting in an increase in miscarriages and chromosomal abnormalities in babies. The most successful method for achieving a pregnancy at advanced female age is via egg donation.