BROOKLYN - Police arrested a man who they say punched a pregnant woman in the face while she was walking down a Bed-Stuy street. 

According to investigators, 33-year-old William Stephens is charged with felony assault after attacking the 34-year-old victim on Monroe Street

They say a witness alerted a passing officer, who was able to immediately put out an alert. Stephen was then caught nearby. 

The woman was taken to the hospital, treated for a head injury and released.