16 Weeks

Your baby now measures about 4.3 to 4.6 inches (10-12 cm) from crown to rump and weighs about 2.8 ounces (79 g). Fingernails are well-formed and the fine hair, lanugo, may be growing on the head. Arms and legs are moving. The nervous system is functioning and muscles are responding to stimulation from your baby's brain. You may be able to hear the baby's heartbeat in the doctor's office.

Within the next few weeks you may start to feel your baby move, called "quickening." It's often like a gas bubble or subtle fluttering movement. As it happens more regularly, you'll know it's your baby.