At week 17, your fetus is between 3 ½-5 ounces and around 5 inches long, and his umbilical cord is getting stronger and thicker to help support his growth. He is creating a better connection to his brain, muscles, and nerves, and his bones are changing from cartilage to ossified bone (getting strong!). If all that wasn't enough to make a fetus tired, he is also putting on the fat that will help him regulate his temperature and eventually look like the newborn we expect to see come his birthday. Bring on the adorable baby chub!
All babies are unique, but part of what makes them truly unique starts to form this week. The swirls and lines on a baby's hands and feet are beginning to form, creating foot and fingerprints and patterns that are utterly unique and will stay with them for the rest of their life. These identifying marks are 100% unique and can be used to identify your baby once they are born. This is why most hospitals will take footprint impressions shortly after birth.