Dr Ashok Chauhan told the BBC the termination would be carried out "anytime now".
The girl became pregnant about five months ago. She alleges rape by her stepfather, who has been arrested.
Indian law does not allow terminations after 20 weeks unless doctors confirm the woman's life is in danger.
The decision to allow the child to abort was taken after a local court told doctors at the Post-Graduate Institute of Medical Sciences (PGIMS) in the town of Rohtak that it would accept their recommendation.