Casey Downie-Campbell 27 November 2023 Family life, Baby Massage The 4th Trimester: Nurturing and Understanding Your Newborn Casey Downie-Campbell 27 November 2023 Family life, Baby Massage The 4th trimester refers to the first three months of a newborn's life outside the womb. It is a time of immense transition, as your little one adjusts to the outside world and their new surroundings.