Pregnancy starts when a sperm fertilises an egg. From that point on pregnancies are divided into three stages called trimesters. Each describes a stage of a baby's development during pregnancy.

In the first trimester, the egg has been fertilised and your body is getting ready for pregnancy. You may feel stretching in your abdomen, experience some sickness and need to pee more frequently as your uterus stretches and begins to press on your bladder.

It's during this time that your baby develops from a bundle of cells into an embryo. Their organs and body parts begin to form as well as the placenta. The placenta is an organ that is attached to the lining of your womb during pregnancy. It's through the placenta that all the oxygen, nutrients and hormones are passed from you to your baby.

In the second trimester, your pregnancy becomes more visible - although the exact timing of this will vary from woman to woman. Usually the sickness that often occurs in the first trimester will get better. You may also feel your baby start to move from around 18 to 20 weeks.

During the second trimester your baby's organs continue to develop. Their ears normally develop by about 16 weeks which means that they will start to hear some sounds. In this time a baby will sleep and wake, and may kick and stretch too.

The third trimester is the final stage of pregnancy. You'll probably feel tired and experience some breathlessness as your bump pushes up towards your lungs.

By this point, most of the baby's major development is complete. The baby's bones will start to harden and they will gain fat.  The baby will also usually turn so that their head is pointing down ready for birth.

Folic acid is a really important supplement for all pregnant mothers. It helps your baby's development and protects them from getting birth defects known as neural tube defects, which can affect babies' brains, spines and nervous systems.

You should start taking it when trying to get pregnant or as soon as you find out that you're pregnant.

Folic acid supplements are taken as a pill. You can also increase your intake of folic acid by making sure you eat lots of green leafy vegetables, brown rice and brown bread. While eating more of these foods is good, it won't give you all the folic acid your baby needs, so make sure that you take the supplements too.

Syphilis is another infection that can be easily passed from mother to baby during pregnancy. It can be very serious for babies and is often fatal. As many as 40% of the babies born to mothers with undiagnosed syphilis will die from the infection.

This is why it is so important to get tested for syphilis during pregnancy. You should be tested for syphilis in your first appointment after finding out that you're pregnant. If the result is positive, syphilis can be treated with antibiotics. This can also stop the infection from being passed on to your baby. If you test negative it's important that you avoid getting syphilis during the rest of your pregnancy, and you should test again if you think you might have been at risk.

Not all babies born with syphilis will show symptoms of the infection, so if you had syphilis during your pregnancy and didn't get treatment, your baby will need to be tested at birth. If they have the infection, it's important that they get treatment right away.