For so many reasons, women want to have babies later in life. But with terms like “advanced maternal age” and references to a ticking time clock, you might be wondering, when and why does fertility really begin to decrease?
How a Woman's Age Affects Fertility
A woman is born with all the eggs she will have in her lifetime. As a woman ages, her eggs decrease in quality and quantity. While good health improves the chance of getting pregnant and having a healthy baby, it can’t completely overcome the effects of age on a woman's fertility.
Some estimates suggest that a woman in her early to mid-20s has a 25–30% chance of getting pregnant each month. Fertility generally starts to slowly decline when a woman is in her early 30s, and after the age of 35 the decline speeds up. By age 40, the chance of getting pregnant in any monthly cycle is around 5%.
What Causes the Fertility Drop in Women?
Unlike men, who are continuously producing more sperm, a woman is born with a fixed number of eggs. Women are born with between one to two million at birth, and by puberty, this amount declines to between 300,000 and 500,000. During the years that a woman is menstruating, she loses several eggs every month.
In addition, it’s not just egg quantity that is declining, it is also egg quality. By age 45 or 50, many of the eggs that remain in the ovaries are chromosomally abnormal and cannot be fertilized. Of the eggs that can be fertilized, many cannot develop and implant into the uterus, and of those that are able to implant, many are miscarried in the first trimester.
The Link Between a Woman's Age and IVF outcomes
In vitro fertilization (IVF) treatment can help couples get pregnant, but a woman's age also affects the chance of success with IVF.
The following represent percentages of live births per retrieval by age:
- Under age 35: 41.3%
- Ages 35-37: 29.7%
- Ages 38-40: 18.2%
- Ages 41-42: 9.1%
- Over age 42: 3.1%
The Link Between a Woman's Age and Pregnancy Complications
The risk of pregnancy complications also increases with age. This includes the risk of chromosomal abnormalities in babies, as well as complications in pregnancies and deliveries, such as gestational diabetes, placenta previa, the need for cesarean section and stillbirth.
How a Man's Age Affects Fertility
Even though men continue to produce sperm throughout their lives, the quality of their sperm declines with age.
What Causes Male Fertility to Drop?
There are several reasons that male fertility declines with age:
- Hormones: Testosterone production decreases, which can impact fertility
- Sperm production: The rate at which sperm cells are produced slows down
- Blood supply: Blood supply to the pelvic area may decrease
- Vas deferens: The tubes that move sperm may narrow
- Oxidative stress: Oxidative stress can impact sperm quality
In addition to age, certain lifestyle factors can impact male fertility, including obesity, poor diet, and exposure to environmental toxins.
What Healthy Habits Can Someone Incorporate to Improve Fertility?
There are ways to help your body prepare to conceive after age 35:
- Maintain a healthy lifestyle centered around nutritious food and regular movement to support a healthy body composition
- Take a comprehensive prenatal vitamin
- Consider supplements specifically formulated to support egg quality and sperm quality
- Discontinue any nicotine or cannabis use and exposure
- Manage stress
- Limit exposure to environmental toxins
- Limit caffeine to under 200 milligrams per day
- Limit or avoid alcohol
What If You are Struggling to Naturally Conceive After 35?
If you’re over 35 and have been attempting to conceive for at least 6 months, or over 40 and have been attempting to conceive for at least 3 months, reach out to your OB or midwife. This can get the conversation started on your goals and next steps in terms of looking into your fertility.
