Many of the bones in your baby's body are starting to harden. Among these first bones to develop is the inner ear which is part of the reason why your baby might be able to hear sounds such as your heart beating or your tummy growling.
As you settle into your second trimester you'll likely gain your appetite back. Eating healthy and getting enough protein is important at this stage as your body needs approximately 300 extra calories to help your baby develop. Equally important is continuing with exercising; keep moderation in mind and do not to begin any new, strenuous workouts.