Society often tells women in their 20s that they’re “too young” to have children. Women are often encouraged to wait until they’ve established themselves in their careers to start their families, which often means that they’re into their mid to late 30s before they even start to consider having children. However, this advice doesn’t really take biology into account. While we would certainly never encourage anyone to have children before they feel ready, it’s important to be aware of the effects of age on fertility, so that you can plan for the healthiest and least stressful path to starting your family.
How Age Affects Fertility
When a baby girl is born, she already has all of the eggs that she’ll ever have in her lifetime. The egg cells remain in the ovaries, with one (or, occasionally, more than one) ripening and being ovulated each month, and the others continuing to wait. Over time, the woman’s supply of healthy eggs, which is known as her ovarian reserve, is used up, and then she will no longer be fertile. (Anything that causes the egg supply to be damaged, such as smoking, accelerates this loss of fertility.)
When a woman goes through menopause, then she will become completely and permanently infertile. For most women, menopause happens in their early 50s. However, the loss of fertility doesn’t occur all at once; rather, there’s a gradual decline in the chances of the woman getting pregnant. For a healthy woman at age 30 who’s not using contraception, there’s about a 20% chance that she’ll become pregnant with each cycle. For the same woman at age 40, the chance of pregnancy is only 5% per cycle. That’s a dramatic difference.
However, the averages conceal a lot of individual variation. The exact rate at which the ovarian reserve disappears differs from one woman to another, depending on genetics, lifestyle, and other factors. If you’re in your 30s or 40s and trying to get pregnant, you might want to get a sense of where your body is along this continuum.
Testing for Age-Related Fertility Loss
There are several different tests that your doctor may recommend to get a sense of how close your body is to depleting your ovarian reserve and going through menopause.
During each menstrual cycle, hormones fluctuate. Estrogens, progesterone, LH, and FSH are the key players in the cycle; prolactin, the hormone of breastfeeding, may block the cycle. Fertility doctors commonly measure estradiol (a form of estrogen), prolactin, LH, and FSH, on the third day of the menstrual cycle. Elevations in the levels of LH, FSH, and/or estradiol indicate that the woman’s ovarian reserve is low. In this case, the woman is less likely to get pregnant using her own eggs.
Another hormone that’s correlated with ovarian reserve is anti-mullerian hormone (AMH). This hormone is produced by ovarian follicles as they begin to mature. By looking at AMH, doctors can get a sense of how many healthy follicles a woman has left; the higher the AMH level, the greater the ovarian reserve. AMH levels have been correlated with IVF success rates and live birth rates.
If a woman’s hormonal testing indicates that she’s less likely to conceive using her own eggs, she doesn’t have to give up on having a baby. Donor eggs are a commonly used option for women whose ovarian reserve is low. The eggs are retrieved from the egg donor, combined in the laboratory with sperm (from the intended mother’s partner, or from a sperm donor), and the resulting embryo is transferred into the uterus of the intended mother. She will then carry the pregnancy and give birth to her child.
If you’re a patient at Reproductive Health Center of Tucson and are interested in learning more about using donor eggs, you can discuss your options with Randi, our Egg Donor Coordinator.
Preimplantation Genetic Screening of Embryos
Recall that a woman’s eggs are as old as she is. As a woman ages, her eggs may suffer from damage to their genetic material. This is why births of children with Down Syndrome and other chromosomal abnormalities are far more common in older mothers than in younger ones; the risk of Down syndrome is 1 in 2,000 for a 20-year-old mother, and 1 in 30 for a 45-year-old mother.
Because of the risk of chromosomal abnormalities in embryos conceived by older women, many couples who are using IVF to conceive their children choose to have preimplantation genetic screening (PGS) of their embryos. This technique analyzes the genetic material of embryos created in the laboratory. This allows the couple to choose to implant only the healthy embryos into the woman’s uterus. Couples in which the intended mother is age 35 or older should discuss this option with their doctors, although younger couples may also choose it.