The third week of pregnancy does not result in a fetus, generally called an embryo, which is about 5mm to 1cm in length and weighs less than 1g. The third week of pregnancy is also just about 1 week after fertilization. The fertilized egg unites and arrives in the uterine cavity after 3 to 4 days of movement, dividing from one cell into multiple cells into a solid mass of cells with a constant total volume, called an embryo. The third week of pregnancy is still relatively short, at this time the length is about 5mm to 1cm, the weight is less than 1g, the head is directly attached to the carapace, there is a long tail, and its shape is very similar to a small seahorse. Three weeks pregnant women should not be too anxious, it takes a period of time to determine through ultrasound examination of the uterine cavity with the development of yolk sac, embryonic buds, fetal heart, before the pregnancy can continue. Do your pregnancy checkups and seek medical attention for any abnormalities.