A hospital room decorated in blue balloons, onesies declaring, “Mama’s Boy,” and adoration from nurses and family members alike: that is a typical welcome scene for a newborn baby boy in the United States. Those first days are often filled with attention, affection, and soothing words for the streams of tears that typify babyhood. In those first days, girls and boys are very much the same. They are free to express pain, fear, and surprise. Parents scramble to learn everything they can to create the most loving, supportive home for their new child. But in the days and years that follow, something changes.