07 Feb Women Often Told Fertility ‘Falls Off a Cliff’ At 35, Is this Correct?
It’s no secret women’s fertility declines with age. But the common description of a rapid decline in fertility at age 35 is more fiction than fact.
If you want to conceive now or in the future, it is important to understand the biology of fertility. This can help those who have a choice about timing to decide when to start trying for a baby. For women who are not ready to start to try for a pregnancy, knowing your options can help you make the best decisions regarding your fertility.
Age, Egg numbers and Quality
Women are born with one to two million eggs in the ovaries and by the time a woman reaches puberty about 300,000 eggs remain. This is a normal physiological process called atresia. The rate of egg atresia is accelerated after age 37 for most women.
Of the eggs that remain when a woman starts having periods, only 300-400 will mature and be released in ovulation during the reproductive years. By the time a woman reaches menopause, there are no more functioning eggs in her ovaries.
As women age, egg quality declines too. It’s estimated about 20 percent of all human eggs are “aneuploid”, which means they have the wrong number of chromosomes. This proportion increases as women age and by age 45 years, the rate of chromosomally abnormal eggs is estimated to be 99 percent.
Conceiving at Different Ages
A woman’s most fertile years are between her late teens and late 20s. By around age 30, fertility starts to slowly decline and by mid-30s the decline in fertility speeds up. However, the decrease in the chance of pregnancy after age 35 is gradual and more like a slope than a cliff, at least until age 40.
A large study that followed women trying for a baby found the chance of pregnancy after 12 months was 87 percent for women aged 30-31. This dropped to 76 percent at age 36-37, and 54 percent at age 40-41.
To learn more about these topics and speak to one of our physicians about fertility treatment, you can request a consultation here.