A packed train in Manhattan quickly turned into a delivery room and straphangers became midwives, as riders banded together to deliver a baby when the mother went into labor while aboard the subway.

According to police, the woman was approached by a person who slashed her across the left cheek and right eyebrow with a box cutter.

A woman was slashed during the Monday evening commute inside an Upper East Side subway station, according to the NYPD. The 28 ...