Sweden's Abeba Aregawi recently failed a doping test in her native Ethiopia and is provisionally suspended.
Both are repeat winners of the road race.
Simpson was contending before the mishap about halfway through the race.
What goes in to being a professional runner?
A day in the life of Jenny Simpson as she trains for Worlds.
Two-time Olympian Jenny Simpson, 28, is one of America’s best runners on the track, having earned world championship gold (2011) and
New Balance squad takes down women's DMR world record. Bernard Lagat shatters Masters 3000m mark.
It's the first time in 12 years distance runners have swept the awards.
The race adjacent to Central Park featured fast times and photo finishes.
The American won the race down one of New York's most famous streets in 2011 and 2013.