Fertility 101

How Age Impacts Your Fertility

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In the U.S., about 20 percent of women have their first child after age 35. But because infertility increases with age, about one third of these women face conception challenges.

Quality and Quantity of Eggs

As women age, their odds of conceiving decline. This phenomenon is largely attributed to reproductive aging, in which both the quantity and quality of eggs, or ovarian reserve, decline over time.

Unfortunately, women begin losing their eggs with time before they can even begin to use them: A 20-week-old fetus has 6-7 million eggs, and this number falls to 1-2 million at birth.

The decline in egg quantity accelerates as a woman enters her late 30s, with a sharp decrease occurring in her early 40s, until she ends up with ~1000 eggs as she enters menopause. Egg quantity is a critical issue for women due to the fact that their bodies are not able to generate new eggs over time, unlike men, who are able to make new sperm every 72 days.

Because women are born with all the eggs they will ever have, egg quality also deteriorates with aging. Egg quality refers mainly to the genetic makeup of the egg. As women age, the machinery that each egg is equipped with to ensure it maintains the right amount of genetic material, or DNA, can break down over time. As a result, older women will have higher proportions of genetically abnormal eggs that are incapable of resulting in a healthy pregnancy.

Additionally, older women are more likely to have accumulated gynecologic or general health issues that could also interfere with their ability to get pregnant. Womens’ menstrual cycles and ovulation may also grow increasingly irregular with age, which can also lead to fertility problems.

Chromosomal Abnormalities and Miscarriage

At least one half of all miscarriages are due to abnormal chromosomes. Eggs are more likely to have genetic abnormalities, such as the loss or gain of one or more chromosomes, as they age. These genetic abnormalities result in the egg not being able to normally grow and develop, and result in abnormal, low quality embryos which may not be capable of normal growth or implantation.

If an abnormal embryo does implant, it has a very high chance of leading to a miscarriage. So, it is no surprise that the incidence of miscarriage also increases significantly with age. Several studies show that a woman under 30 years old has a 5 percent chance of having a miscarriage. For women 35-39 years old, that risk increases to 16 percent. If you’re 44-46 years old, you have a 60 percent chance of having a miscarriage.

IVF Success and Age

One way to try to overcome the effects of aging on fertility is through the use of fertility treatments like in vitro fertilization (IVF). Technological advances in the field of reproductive medicine, such preimplantation genetic testing (PGT), have provided IVF clinics with the ability to accurately analyze the number of chromosomes in an embryo.

PGT allows for the identification of healthy, genetically normal embryos in order to maximize pregnancy rates and reduce the risk of miscarriage. When older women use genetically tested embryos to conceive, their chances of becoming pregnant become equivalent to that of a younger women. In women approaching their mid- to late 40s, it can become increasingly difficult to find genetically normal eggs and/or embryos when they undergo IVF. For these patients, egg or embryo donation may be recommended to provide the best chance for conceiving and carrying a pregnancy.

Dr. Jovana Lekovich is a board-certified obstetrician and gynecologist and reproductive endocrinologist and infertility specialist. She is the Director of the Oncofertility Program atBlavatnik Family- Chelsea Medical Center at Mount Sinai. Dr. Lekovich is an assistant clinical professor at the Icahn School of Medicine at Mount Sinai in New York, where she specializes in treating all aspects of reproductive medicine and infertility, including conditions such as amenorrhea, polycystic ovary syndrome, and diminished ovarian reserve with ovulation induction, intrauterine insemination, in vitro fertilization, intracytoplasmic sperm injection and preimplantation genetic testing of embryos. She also uses minimally invasive techniques suchas laparoscopy and hysteroscopy to treat a variety of surgical conditions including endometriosis and uterine factor infertility. 

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