Women's Health Matters

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Fertility and age

Women’s fertility is limited by time. Fertility changes over the course of women’s reproductive lives, decreasing as they get older. A woman’s ability to get pregnant starts to decline many years before she reaches menopause.

It’s important for women to be aware of this timeline.

“Fertility peaks in women in their late 20s or early 30s, and begins to decline around age 35,” says Dr. Sony Sierra, a gynecologist at Women’s College Hospital who specializes in reproductive endocrinology and infertility

“At that age, there is a decrease in the pregnancy rate, as well as an increase in the miscarriage rate,” Dr. Sierra explains. “Those are both related to the same mechanism, which is egg quality and the ability of a woman’s eggs to divide and multiply and be chromosomally normal.”

There is a sharper decline in fertility at age 38. After age 40, many women will have trouble conceiving. Dr. Sierra notes that the chances of getting pregnant naturally after age 40 are around five per cent per cycle. That’s a one in 20 chance every month. In comparison, a woman under 35 has a 20 per cent chance – or one in five – of getting pregnant per cycle.

“With many women having children later in life now, those figures are becoming more relevant,” Dr. Sierra says. “The age at first pregnancy has increased over the past decade, and it’s becoming more common for women to want to start a family in their mid-thirties.”

Risks for older women

Older women not only have more trouble conceiving, but also have higher pregnancy risks.

“There is a greater risk of miscarriage because egg quality diminishes,” Dr. Sierra says. “For the same reason, there is also a higher risk of chromosomal abnormalities, such as Down syndrome.”

Women over 40 also have a higher chance of pregnancy and delivery complications, including:

  • high blood pressure
  • gestational diabetes
  • need for a cesarean section

Women over 40 are also more likely to have babies with low birth weights.

“So there are a lot of things to consider for older women who want to get pregnant,” Dr. Sierra says.

“For younger women who don’t want a family yet, fertility may not be foremost in their minds,” she adds. “But women of all ages deserve to have an understanding of how fertility changes over time, and how that can affect them.”


This information is provided by Women’s College Hospital and is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition. This document was last reviewed on: August 22, 2014

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