Massof graduated from medical school in Grenada in 1998 and passed some tests necessary to become a physician in the U.S., but never obtained a medical license.
Another defendant, Lynda Williams, 43, of Wilmington, also may plead guilty during a status hearing next week. That hearing is scheduled for next Wednesday before Lerner.
Williams, who was an unlicensed clinic worker from 2008 to February 2010, when authorities raided the facility, is facing charges that include the murder of a viable baby and the third-degree murder of a 41-year-old woman who died of a drug overdose given to her at the clinic.
Prosecutors and defense attorneys can't comment on the proceedings outside of court because Lerner has placed them under a gag order.
If Lerner accepts guilty pleas from Massof and Williams that would leave just five defendants to be tried. Those who have pleaded guilty could attempt to win less harsh sentences by cooperating with prosecutors and testifying against their co-defendants, who include Gosnell, 70, and his wife, Pearl, 50.
Gosnell, who owned the now-shuttered Women's Medical Society on Lancaster Avenue, faces the most legal jeopardy.
The District Attorney's Office contends that he is responsible for the first-degree murders of seven babies born viable and alive at his clinic. The babies' spinal cords were cut, prosecutors allege. He also is charged with third-degree murder in the death of the 41-year-old overdose victim.
Prosecutors have said they will seek the death penalty against the doctor if he is convicted of first-degree murder.