Directions: BWI Marshall has family restrooms in many locations throughout the terminal building. There are four on Concourse A - one before security between security and the bank, one just past security near the Phillips restaurant, one at gate A9 and one in baggage claim on the lower level. There are five family restrooms in the Concourse B area - one at security, one near the Silver Diner restaurant, one at gate B2, another at gate B7 and one at baggage claim belt 5. Concourse C has two family restrooms - one in the upper level back hallway near the Lost & Found office and one at gate C7. There are four near Concourse D - one is in the upper level back hallway near Bill Bateman's restaurant, one in the back hallway behind the Air Tran Airways ticket counter, another at gate D7 and one at baggage claim belt 12.
Comments: i've only used the family bathroom near the M&T Bank, a janitor unlocked the door for me. the door closed automatically (it took a few seconds) and has a manual lock on it. I think the family bathrooms are usually open/available for use but I'm not sure. I don't know which ones are accessible.