There is tremendous growth in the baby this week. In the beginning of the 7th week the crown to rump length of your baby is .16 to .2 inches which doubles by the end of the week to 0.44 or 0.52 inches. This is the stage where all the essential organs are beginning to form within the embryo such as the hair, nipple follicles, the eyelids and the tongue. The elbows and toes become more visible after the trunk starts becoming straight. The baby is about the weight of a pea or an Asprin tablet. The placenta begins to show after this week and the head is larger than the other body parts. The internal organs have already formed and the heart has begun beating from the end of the 4th week. The baby is floating in the amniotic sac and the buds for the arms and legs have emerged in the 5th week and in the 7th week the buds for the fingers and toes also start appearing. The umbilical cord is growing in length and will continue to grow giving the baby freedom to move in the stomach. The embryo has now grown fully into a fetus. If you calculate this period as the 7th week of pregnancy from conception the muscles and nerves start functioning. The baby develops reflexes and can move. The abdomen and thorax are fully formed and the lungs have started developing. The heart which is now in the thoracic cavity beats strongly and the head becomes more outstanding as it starts leaning towards the body. The mouth can be opened and the eyes can be seen behind the closed membranes. You can even notice fingers, ears and the vestibular system developing.