Philadelphia (CNN) -- A worker at a west Philadelphia abortion clinic has pleaded guilty to two counts of murder and may testify against Dr. Kermit Gosnell, the doctor accused of performing illegal late-term abortions, court officials said.
Lynda Williams, a former employee of Gosnell's Women's Medical Society clinic, entered a guilty plea Wednesday to six charges, including two counts of third-degree murder.
The first charge is for the 2009 death of an aborted fetus that the Philadelphia district attorney's office claims in a grand jury report was born alive. The second is the death of 41-year-old Karnamaya Mongar, who died in a second-trimester abortion, according to Common Pleas Court Judge Benjamin Lerner.
Mongar died November 19, 2009, after overdosing on anesthetics prescribed by Gosnell, according to Philadelphia District Attorney Seth Williams.
The other charges Williams pleaded guilty to are delivery of drugs illegally causing the death of another human being, engaging in corrupt organization and two counts of conspiracy to corrupt.
Williams is the fifth person to plead guilty in this case. Gosnell's wife, Pearl, is being charged as a co-conspirator.
Lerner said that the district attorney's office is expecting Williams to testify.
The Philadelphia district attorney's office grand jury report from January 11, 2011, charged Kermit Gosnell with murder for allegedly performing abortions past the 24-week limit prescribed by law. The report says scissors were used to sever infants' spinal cords. He faces eight counts of murder in the deaths of seven babies and Mongar.
Prosecutors filed a pleading saying they intended to seek the death penalty against him.
There is a federal criminal investigation into the abortion clinic deaths, and Williams may face federal violations.
Williams' sentencing hearing is scheduled for December 20.
CNN's Kristina Sgueglia contributed to this report.