Alvin Vallejo, a public health nurse in San Francisco, steps inside a dilapidated apartment building in the Tenderloin neighborhood.
He climbs a narrow staircase to visit a client on the third floor recovering from a high-risk pregnancy and a difficult birth. Vallejo turns down the hall, passes a communal bathroom, and knocks on a door.
Dayanis, a 35-year-old mother cradling a newborn dressed in a turquoise onesie, answers the door. (Only her first name is used to protect her medical privacy.)