This week your baby weighs a little over 4 pounds and has passed the 17-inch mark. She's rapidly losing that wrinkled, alien look and her skeleton is hardening. The bones in her skull aren't fused together, which allows them to move and slightly overlap, thus making it easier for her to fit through the birth canal. (The pressure on the head during birth is so intense that many babies are born with a conehead-like appearance.) These bones don't entirely fuse until early adulthood, so they can grow as her brain and other tissue expands during infancy and childhood.