Age and Fertility

Age affects the fertility of both men and women. It is the single biggest factor affecting a woman’s chance to conceive and have a healthy baby. A woman’s fertility starts to decline in her early 30s, with the decline speeding up after 35.

Age and fertility

Male fertility decline is more subtle, but a man’s age affects the chances of his (female) partner conceiving, and increases the risk of miscarriage and the child’s risk of mental health and developmental disorders.

While it’s important to be aware of the effect of age on fertility, other factors also play a role. Being a healthy weight, having a balanced diet and exercising regularly, not smoking, protecting yourself against sexually transmitted infections, and knowing when in the menstrual cycle a woman is most likely to conceive, will all improve your chance of conception.

Women’s age and fertility

A woman is born with all the eggs she is going to have in her lifetime. Her eggs will decrease in quality and quantity as they age with her. This is the reason that age is the single most important factor affecting a woman’s fertility. While good health will help with conception and having a healthy baby, it will not override age as a factor affecting a woman’s fertility.

In her early to mid 20s, a woman has a 25-30 per cent chance of getting pregnant per month. A woman’s fertility generally starts to decline in her early 30s, with the decline speeding up after 35. By age 40, her chance of getting pregnant in any monthly cycle is down to five per cent. Fertility research conducted among the Hutterite women of North America, who don’t use contraception, found that 11 per cent of women were infertile by age 34, 33 per cent by age 40 and 87 per cent by age 45.

In a survey of more than 3,000 childless women, 65 per cent believed that before menopause, assisted reproductive technologies such as IVF can help most women to have a baby using their own eggs. However, a woman’s age also affects the chance of success with IVF.

In 2011, in Australia and New Zealand, the chance of a live birth per IVF cycle was 26.6 per cent for women aged under 30, 16.9 per cent for women aged 35-39, and 6.6 per cent for women aged 40-44. For women over 45, this dropped to 1.2 per cent.

A woman’s age not only affects her chance of conceiving. It also increases the risk of pregnancy loss. In a study of more than one million pregnancies which were intended to go to term, 9 per cent of women aged 20-24 experienced pregnancy loss compared with 54 per cent of women aged 42 or more.?

A comparison of women aged less than 30 and older than 40 shows that the risk of chromosomal abnormalities in the fetus increases from 1 in 385 to 1 in 63.

Men’s age and fertility

Male fertility generally starts to decline after 40 when sperm quality decreases. Increasing male age reduces the overall chances of conception, and increases time to pregnancy, the risk of miscarriage and the risk of the child developing mental health disorders. There is strong evidence that increasing male age also correlates with increasing DNA fragmentation.

In one study of more than 8,000 pregnancies, after adjusting for female age, conception during a 12-month period was 30 per cent less likely for men over age 40 years, compared with those younger than 30.

There is an increased risk of miscarriage and fetal death with higher paternal age. Data from 23,821 pregnant women in the Danish National Birth cohort showed that pregnancies fathered by men aged 50 or older had almost twice the risk of ending in fetal death.

Children of fathers aged 40 or over are five times more likely to develop an autism spectrum disorder than children of fathers aged 30 or less.Children of older fathers are also at increased risk of schizophrenia and other mental health disorders, and mental retardation.