16 Weeks

Your baby is now about the size of an avocado (about 5 inches / 11.6 centimeters long from crown to rump and weighing approximately 4 ounces / 100 grams). In the next three weeks he'll go through a tremendous growth spurt, doubling his weight and adding inches to his length.

In or out of the womb, babies are playful creatures. Yours may already have discovered his first toy - the umbilical cord - which he'll enjoy pulling and grabbing. Sometimes he may even clutch it so tight that less oxygen gets through, but don't worry - he doesn't hold onto it long enough to harm himself. The circulatory system and urinary tract are in full working order, and he's inhaling and exhaling amniotic fluid through his lungs.

Sometimes, when you move suddenly, you may a feel a slight pain in your sides. Ligaments on each side of your uterus and pelvic walls are stretching as your baby grows. It's normal to feel some pain, but if it continues for a few days or escalates, talk to your doctor.