Your baby weighs in at one pound, six ounces, and measures 21 centimeters crown to rump. Rapid eye movement has begun. She can hear everything now, and also has a sense of equilibrium. She can tell the difference of what would feel upside down as opposed to right side up, even in such a small amount of space to move around! Now that she's almost completely formed, your baby will build up body fat to help her retain heat.