This is a detailed scan, usually carried out at 18-20 weeks of pregnancy, that checks for possible physical problems (abnormalities) in your baby, although it can't pick up every problem.

The scan is offered to all women, but not everyone chooses to have it. Your choice will be respected if you decide not to have the scan, and you'll be given the chance to discuss it with your maternity team before making your decision.

You may be asked to drink some fluid so that your bladder is full before you have the scan. A full bladder pushes your womb up and can give a clearer picture. You then lie on your back and some jelly is put on your abdomen. A probe is passed backwards and forwards over your skin and high-frequency sound is beamed through your abdomen into the womb.

The sound is reflected back and creates a picture that's shown on a TV screen. Sometimes, the sonographer doing the scan will need to be quiet while they concentrate on checking your baby. But they will be able to talk to you about the pictures once they've completed the check.

Most hospitals welcome partners into the scan room. Many couples feel that the scan helps to make the baby real for both of them. It's often possible to have a copy of the picture. (There may be a small charge for this.)