Week 31

He's entering a growth spurt. For the next eight weeks, he'll gain weight faster than he increases in length, at the rate of about half a pound a week. The bigger he gets, the harder it will be to "see" him on ultrasound and get a good estimate of his size--the margin of error increases to 15 percent by the end of the third trimester. But he's definitely growing fast, and you'll notice that his kicks will start to feel more like squirming as he runs out of room to roam.