39 weeks

How your baby's growing: Your baby's ready to greet the world! He continues to build a layer of fat to help control his body temperature after birth, but it's likely he already measures about 20 inches and weighs a bit over 7 pounds. (Boys tend to be slightly heavier than girls.) Your baby's organs are fully developed and in place, and the outer layers of skin are sloughing off as new skin forms underneath.