Some women fall pregnant quickly, while for others it may take some time.

In every 100 couples trying for a baby, the woman will get pregnant within one year in 80 to 90 cases. The rest will find it takes longer, or they may need help to conceive.

What happens when you fall pregnant

For a woman to get pregnant, a man’s sperm must fertilise her egg. A woman releases an egg from her ovary once every month. This usually happens about 14 days before the first day of her next period.

Most women ovulate each month. Occasionally, more than one egg is released, usually within 24 hours of the first egg. At the same time, the lining of the uterus (womb) begins to thicken and the mucus in the cervix becomes thinner so that sperm can swim through it more easily. The egg begins to travel slowly down the Fallopian tube, a tube that stretches from the ovary to the uterus.

If there has been recent sexual intercourse with ejaculation by the man, the egg is most likely to be fertilised in the Fallopian tube. The lining of the uterus is now thick enough for the egg to be implanted in it after fertilisation.

The level of the hormones oestrogen and progesterone changes in a woman’s body during pregnancy. As soon as she has conceived, the amount of oestrogen and progesterone in her blood increases. This causes the uterus lining to build up, the blood supply to the uterus and breasts to increase and the muscles of the uterus to relax to make room for the growing baby.

If the egg is not fertilised, it passes out of the body during the woman's monthly period, along with the lining of the uterus, which is also shed. The egg is so small that it cannot be seen by the naked eye.

Increasing your chance of falling pregnant

There are 2 ways you can increase your chances of falling pregnant:

• Calculate when you will ovulate and have unprotected sex 1 or 2 days before that date.
• Make sure both you and your partner improve your health, diet and lifestyle.

An egg can be fertilised for about 12-24 hours after it's released. You're most likely to get pregnant if you have sex within a day or so of ovulation.

Try not to get too stressed about falling pregnant. Having unprotected sex every couple of days around the time of ovulation is the best way to make sure there is always a good supply of sperm to fertilise the egg when it's released.

Many factors can affect your chances of falling pregnant. These include your age and your partner's age, your lifestyle, your weight, whether either of you has a chronic illness, and how often you have sex.

If you are under 35 and you are not pregnant after a year of having unprotected sex, see your doctor. If you are over 35, it is a good idea to seek help sooner.

Confirming your pregnancy

A pregnancy test measures the hormone human chorionic gonadotrophin (hCG). You can buy a home pregnancy test from a pharmacy and use it 4 days before your next period is due.

If you think you might be pregnant, see your doctor after you have missed a period. They will confirm the pregnancy and give you advice about looking after yourself and pregnancy care.

Will it be a boy or girl?

Both the man's sperm and the woman's egg play a part in determining the gender of a baby.

Every normal human cell contains 46 chromosomes (23 pairs). Chromosomes are tiny threadlike structures made from DNA, which each carry human genes. Genes determine a baby's inherited characteristics, such as hair and eye colour, blood group, height and build.

When a sperm fertilises an egg, 23 chromosomes from the father pair with 23 from the mother, making 46 in total.

The sex chromosome from a woman's egg is always the same and is known as the X chromosome. But the sex chromosome from a man's sperm may be an X or a Y chromosome.

If the egg is fertilised by a sperm containing an X chromosome, the baby will be a girl (XX). If the sperm contains a Y chromosome, the baby will be a boy (XY).

Healthy lifestyle

If you’ve decided to have a baby, you and your partner should make sure you’re both as healthy as possible. This includes eating a healthy balanced diet, stopping smoking and, for the woman, taking a folic acid supplement.

You should also know about the risks of alcohol in pregnancy. Seeking health advice from a health professional in helping you prepare for getting pregnant may assist.