0-4 weeks pregnant

After one month, the embryo is less than 1⁄2 cm (around 1⁄4 in) long but the cells are rapidly multiplying

Your body

Congratulations! You may not even realise it yet, but you're pregnant. Pregnancy is actually dated from the first day of your last period, so conception is said to happen in week 3.

Although you won't yet have any external signs, internally your body is already hard at work, preparing for the next nine months...

What's happening to your uterus

Your uterus (womb) normally weighs about 60g (2.5oz) and is 7.5cm (3in) long. But as soon as conception occurs, increased quantities of oestrogen make your uterus grow. The lining thickens to form a deep, juicy layer, in which the embryo can implant, and new muscle fibres begin to form in preparation for giving birth!

What's happening to your cervix

Your cervix (the neck of the uterus) increases slightly in width, becomes softer and deepens in colour due to the increased blood supply and the effects of the oestrogen. Glands in the cervix form a thick mucus plug that seals off the uterus and protects your growing baby from infection.

No more periods!

You've already had your last period for the next few months! As soon as the embryo implants, chemical messengers halt your menstrual cycle. However, you may experience some 'spotting' as the embryo attaches itself to the wall of your uterus.

Next page: Find out more about your baby at 0-4 weeks...