Week 4: your baby has settled into the womb

In the fourth obstetric week, the event that truly starts a pregnancy takes place: the embryo implants in the wall of the womb. It is about the size of a poppy seed, yet its cells are already sorting into the layers that will become every organ, and they are beginning to build the future placenta.

These cells produce the hormone hCG. Its level climbs quickly, and around the day your period is due a home test may show two lines. If the line is faint or the test is negative but your period still hasn't come, repeat it in two or three days.

Many women feel nothing yet; others notice mild pulling low in the tummy, tender breasts or tiredness. Light spotting can happen too. Bleeding or strong pain low in the abdomen, however, is a reason to see a doctor straight away.

What to do this week:

• start or continue folic acid, exactly as your doctor advises;
• book a visit to the antenatal office of your family polyclinic so you are registered before 10 weeks.