The fourth trimester begins when your baby is born and continues until she reaches 3 months old. It's a time of adjustment for both the mother and the newborn -- who was quite content for 9 months inside the womb and now must learn to adapt to all new sights, sounds, and activities. Here are 5 pediatrician-recommended ways to re-create that feeling of being inside the womb during your baby's first 3 months of life.The fourth trimester begins when your baby is born and continues until she reaches 3 months old. It's a time of adjustment for both the mother and the newborn -- who was quite content for 9 months inside the womb and now must learn to adapt to all new sights, sounds, and activities. Here are 5 pediatrician-recommended ways to re-create that feeling of being inside the womb during your baby's first 3 months of life.