After the age of 30, the number of eggs a woman has reduces significantly. After 30 it goes to 20% chance of pregnancy with around 100,000 eggs, 31 it goes to 80,000, 32 to 75,000 and at 35 around 50,000. After 35 your chance of pregnancy drops further to around 25,000 by 37 years of age.
Women in their early thirties are generally better off than women in their late thirties as ovarian reserve declines sharply in the late thirties. For example, a woman at 30 often has around 100,000-150,000 eggs in reserve. By 35, that number is likely around 80,000.
Both egg quantity (the number of eggs a woman has available for fertilisation also called as ovarian reserve) and egg quality (the eggs that are genetically normal) decrease as woman ages. This decrease starts to accelerate by age 35 to 37 and dramatically decreases after age 40.
Even in a woman's 20s to early 30s, approximately 25-30% of the embryos that form from their eggs are anticipated to have genetic errors. This proportion rises to ~50% by age 37-38 and to over 70% at age 40 and beyond.
But age 35 is not without significance. Fertility declines with age due to two factors: a decrease in egg count, as women lose eggs each month; and a decrease in egg quality, as naturally, with age, their eggs are more likely to contain chromosomal abnormalities (mistakes in their DNA).
For women, getting older is something to be more aware of if they wish to conceive naturally. A study revealed that women aged 35-39 had a 29% of conceiving on their most fertile day.
Graphic 3 shows that on average there is a decline in female fertility starting in the mid-thirties, with lower fertility especially after the age of 35. Women's fertility will continue to decrease every year, whether or not she is healthy and fit because the number and quality of the eggs decreases with age.
Supplements containing Myo-inositol, folic acid and melatonin have been shown to help improve egg quality and ovarian function.
The study published by the University of St. Andrews and Edinburgh University in Scotland found that women have lost 90 percent of their eggs by the time they are 30 years old, and only have about 3 percent remaining by the time they are 40.
The woman's age has a crucial importance for egg quality. This fact cannot be emphasized enough. Studies have shown that the ability to have children for women aged 36 are only half as good as in women who are 20 years of age.
Because women in their late 30s and 40s have a higher percentage of abnormal eggs, it's much more likely that their one egg each month will be abnormal. That's why natural fertility declines with age, and why we see infertility, miscarriage, and genetic disorders more often with women over 35.
The decline in both egg quantity and quality may manifest in a longer time to conception. As a result, fecundability–the probability of achieving a pregnancy in one menstrual cycle– begins to decline significantly in the early 30s, with a more rapid decline after the age 37.
Irregular period cycle and difficulty conceiving
If you are facing issues conceiving and have not been able to conceive for a while now, it could be one of the signs of bad egg quality.
On average, women in their mid 20s to early 30s have around 12 to 30 antral follicles, while women aged 35 to 40 may have between 8 and 15 and women aged 41 to 46 may have somewhere between four and 10.
At the age of 37, the average woman has around 25,000 eggs left, and by the time she reaches 51, this will have fallen to 1,000. “Just before menopause, your egg supply reaches below 1,000, and ovulations space out before they stop altogether, eventually,” says Dr. Sekhon.
Women lose 90 per cent of the eggs in their ovaries before the age of 30, new research has shown. The mathematical model shows that the average woman has only 12 per cent of her eggs left by the age of 30 and only three per cent by the age of 40.
A woman is born with all her eggs. Once she starts her periods, 1 egg develops and is released during each menstrual cycle.
After age 35, there's a higher risk of pregnancy-related complications that might lead to a C-section delivery. The risk of chromosomal conditions is higher. Babies born to older mothers have a higher risk of certain chromosomal conditions, such as Down syndrome.
Egg quality is not a scale of healthy to unhealthy, with measures in between—it's a binary state of either normal or abnormal. Once an egg divides with abnormal DNA, it can't be fixed medically or “healed.” In other words, once an egg becomes abnormal, it can't become normal again.
Although age is the main factor affecting egg quality, some diseases, medications, genetic and environmental factors may also cause lower egg quality. Endometriosis, commonly known as chocolate cyst, is among the causes of egg poor quality.
Even with all the understandable talk of “windows of opportunity” and “biological clocks,” there are ways for women over 35 to make motherhood a reality. Infertility treatments can be difficult and expensive, but fertility specialists can talk with you about options. Age is less of a limitation than it used to be.
Look for changes in your vaginal fluids that occur around cycle days eight to 14 (the days leading to ovulation, assuming a 28-day cycle). Ideally, you want to see a clear, slippery fluid that resembles raw egg whites (this is caused by the increased estrogen levels mid-cycle).
The main cause of poor egg quality is age, but it is not the only one; there can be other reasons too, including but not limited to pelvic radiation, ovarian surgery, any reproductive illness, genetic abnormalities, chemotherapy, excess consumption of tobacco, alcohol, and some unknown factors.