Late one night in August 1997, Lenn Rockford Hann placed two bottles of Gatorade near Concourse F of Chicago O’Hare International Airport, unlaced his sneakers, removed his socks, then dodged curious workers for two hours while running 13.1 miles (21.1 kilometers) on the walkways.

Battling cancer is risky for anyone, but when the patient is also a mom-to-be, doctors face a host of unanswered questions.