Measuring more than 10.5" (27 cm) long from crown to rump and weighing nearly 3 lbs (1,300 g), your little one is really starting to put on weight--a very good thing! Her senses of sight and hearing are becoming more fine-tuned this week. She's doing a lot of blinking due to her newfound ability to respond to light and dark, and she can now discriminate between high- and low-pitched sounds, so she'll appreciate your lovely singing voice even more. Baby's bone marrow is now producing red blood cells in abundance.

Although they aren't yet performing the function of obtaining fresh oxygen for your baby's body, her lungs are nevertheless metabolically active. The alveoli, or air sacs, have now filled with lung fluid that is different from amniotic fluid. This special fluid will help your baby to empty her lungs at birth in preparation for that first breath.