• Age affects the fertility of men and women.
• Age is the single biggest factor affecting a woman’s chance to conceive and have a healthy baby. 
• A woman’s fertility starts to reduce in her early 30s, and more so after the age of 35.
• The risks of pregnancy complications increase as women age.
• Male fertility decline is more subtle, but a man’s age affects the chances of his (female) partner conceiving. Male age over 45 years increases the risk of miscarriage, and the child’s risk of mental health and developmental disorders.

A woman is born with all the eggs she is going to have in her lifetime. Her eggs age with her, decreasing in quality and quantity. Age is the single most important factor affecting a woman 's fertility. While good health improves the chance of getting pregnant and having a healthy baby, it doesn 't override the effects of age on a woman 's fertility.

A woman in her early to mid-20s has a 25–30% chance of getting pregnant every month. Fertility generally starts to reduce when a woman is in her early 30s, and more so after the age of 35. By age 40, the chance of getting pregnant in any monthly cycle is around 5%.

It's a common misconception that IVF treatment can overcome age-related infertility. A woman's age also affects the chance of success with IVF. In Australia, the chance of a live birth from one complete IVF cycle (which includes all fresh and frozen-thawed embryo transfers following one ovarian stimulation) is about:

• 43% for women aged 30 to 34 years
• 31% for women aged 35 to 39 years
• 11% for women aged 40 to 44 years.

For older women the chance of having a baby increases if they use eggs donated by a younger woman.

The risk of pregnancy complications increases with age too. The risk of miscarriage and chromosomal abnormalities in the fetus increase from age 35. Complications such as gestational diabetes, placenta previa (when the placenta covers all or part of the cervix, which increases the risk of the placenta detaching), cesarean section and still birth are also more common among older women than younger women.

Conditions that may affect a woman 's fertility include endometriosis and polycystic ovary syndrome (PCOS).

While the effects of female age on fertility have been known for a long time, more recent studies have found that the age of the male partner also affects the chance of pregnancy and pregnancy health.

Male fertility generally starts to reduce around age 40 to 45 years when sperm quality decreases. Increasing male age reduces the overall chances of pregnancy and increases time to pregnancy (the number of menstrual cycles it takes to become pregnant) and the risk of miscarriage and fetal death.

Children of older fathers also have an increased risk of mental health problems (although this is still rare). Children of fathers aged 40 or over are 5 times more likely to develop an autism spectrum disorder than children of fathers aged 30 or less. They also have a slightly increased risk of developing schizophrenia and other mental health disorders later in life.