WEEK 17-18

Week 17: Fat accumulates
Fat stores begin to develop under your baby's skin this week. The fat will provide energy and help keep your baby warm after birth.
Week 18: Baby begins to hear
As the nerve endings from your baby's brain "hook up" to the ears, your baby may hear your heart beating, your stomach rumbling or blood moving through the umbilical cord. He or she may even be startled by loud noises. Your baby can swallow this week, too.

Week 17
How Big is the Baby at 17 Weeks Pregnant?Your baby is anywhere from 4.4 to 4.8 inches by pregnancy week 17 and weighs almost 3 ½ ounces! If you were to hold your baby at 17 weeks pregnant, she would fit snuggly in the palm of your hand. Your baby is about the size of a small pomegranate by pregnancy 17 weeks.
Your Baby's Growth and DevelopmentYour baby during week 17 is now very mobile, gleefully moving his joints here, there and everywhere and will continue to do so as you continue your pregnancy week by week. The cartilage making up the skeleton in your baby's body is starting to transform into bone. At pregnancy 17 weeks time your baby should be hearing things. Your baby will start putting on some layers of fat in the weeks to come, though at this point in time your baby is made up of primarily water.
You may be feeling your baby move intermittently after pregnancy week 17, though as your pregnancy progresses you will likely start feeling your baby move more and more.