Marirosa Anderson was still sweating from a workout when her cell phone rang at 8:20 p.m. on Nov. 11, a particularly cold night in northern Virginia. Anderson had planned to spend the evening with her husband and two small children. Then she saw the caller-ID number. She took a deep breath, readied herself and answered the phone. Karen Harvey, a labor-and-delivery nurse at Inova Fairfax Hospital, gave her the rundown. A baby was about to be delivered by C-section and the parents wanted photographs. Could she come right over?