Your baby has grown significantly and now weighs over 100 grams (3.5 ounces) and is about 17 to 19 cm (6.7 to 7.5 inches) long (crown to rump). They are developing a layer of fat, which will help regulate their body temperature after birth. With the help of a special stethoscope, you can now hear your baby's heartbeat! Brown fat, a special type of fat that can be converted into energy to keep the baby warm, is being deposited. Two basic reflexes, sucking and swallowing, have developed. By birth, babies have nearly all the reflexes that we have as adults. If you're having a girl, tissues are developing into the uterus and vagina. If it's a boy, these same tissues are forming the penis and prostate, with testosterone playing a key role in this development. The baby's crown-to-rump length is 11 or 12 cm (5 inches). The circulatory system is completely functional, and sweat glands are developing. The eyes and ears are in their proper place.