What happens during pregnancy weeks 1 to 3? Your weeks of pregnancy are dated from the first day of your last period. This means that in the first two weeks or so, you aren’t actually pregnant – your body will be preparing for ovulation as usual. You ovulate (release an egg) around two weeks after the first day of your period (depending on the length of your menstrual cycle).
During the third week after the first day of your last period, your fertilised egg moves along the fallopian tube towards the womb. The egg begins as a single cell, which divides again and again. By the time the egg reaches the womb, it has become a mass of more than 100 cells, called an embryo. Once in the womb, the embryo burrows into the lining of the womb. This is called implantation.