Weeks 13 to 16
The fetus grows very quickly during weeks 13 to 16 - doubling in size from 5 to 10 centimetres. The face starts to form, and by 14 weeks (the 16th week of pregnancy) the eyes can move. The eyelids stay closed until the final two months of pregnancy. Now that the internal organs are in their final positions, the bones begin to harden, although they remain flexible until after the baby has been born.
