Your baby is over 5 inches long and weighs over 100g. His cartilage is turning into bones, and the bones are getting stronger (ossification). Eyebrows and the hair on your baby’s scalp are growing. The baby might experience bouts of the hiccups. Brown fat starts to develop under your baby’s skin; it will help keep your baby warm after birth. Fat also helps regulate the body’s temperature and metabolism. Your baby will continue to add layers of fat as your pregnancy progresses. His umbilical cord is lengthening and becoming thicker and stronger. His hearing also develops; his ears have fully formed. His sweat glands start to develop. His heart continues to beat at 140-150 beats per minute. He continues to improve his sucking and swallowing skills.