This is day 7 of your menstrual cycle

Your age matters when you're trying to conceive, because fertility changes as you get older.

273 days until your due date

You're likely to ovulate in about a week. You were born with all the eggs you'll ever have, with no more than about 400 left in your ovaries by puberty, and no new ones are made. So it's no surprise that fertility falls with age.

Women are generally most fertile between 20 and 24. Although most women have periods into their early 50s, fertility gradually declines through the 30s, 40s, and 50s, while the rates of chromosomal abnormalities and miscarriage rise. Even so, thousands of babies are born to women in their late 30s and 40s every year, and conception is possible even later, which is why doctors advise menopausal women to use contraception for two years after their last period.

If you're hoping to start a family, assume fertility drops sharply after 35. Egg quality also changes with age: about 17 percent of eggs have a chromosomal abnormality in the early 20s, rising to over 75 percent in the 40s. These abnormalities increase the chance of conditions such as Down syndrome.

If you're worried about your fertility, blood tests can indicate how much ovarian function you have left. Some tests measure FSH and estrogen, while newer ones use markers such as anti-Müllerian hormone (AMH) and inhibin B.

But making a baby takes more than releasing an egg. The egg has to travel down the fallopian tube, be fertilized, implant, and the pregnancy must be maintained. The father's contribution counts too.

As a matter of fact

The sperm's long journey

Sperm have to travel a hard 12–16 in (30–40 cm) to reach the egg, which is why so many are produced. Each ejaculation contains about 2–8 ml of semen, with over 40 million sperm in every milliliter.

Good to know

The male biological clock?

Men can make sperm for most of their lives, so you might not expect male fertility to fall much, and plenty of older fathers seem to prove it.

However, recent French research found that men over 35 took much longer to get their partners pregnant, and when they did, the risk of miscarriage was slightly higher. This is because older men's sperm is more likely to carry damaged DNA. Older couples still conceive, but men, like women, pass their peak fertility.

Explainer

The follicle before ovulation

The developing follicle sits just below the surface of the ovary and bulges out just before ovulation. It is most likely to burst and release its egg mid-cycle, around days 13–14 of a 28-day cycle.

This is general information based on NHS guidance, not medical advice, and every pregnancy is different. Talk to your midwife or GP about anything that worries you. If your baby's movements slow down or change, or you have bleeding, severe pain or leaking fluid, call your maternity unit straight away. In an emergency, call 999.