At 20 weeks pregnant, baby is the size of a banana. He or she weighs about 280g and measures about 165 millimeters crown to rump. Your baby is swallowing more these days, which is good practice for his digestive system. He’s also producing meconium, a black, sticky by-product of digestion. This gooey substance will accumulate in his bowels, and you’ll see it in his first soiled diaper (some babies pass meconium in the womb or during delivery).