District Judge R.H. Wallace ordered John Peter Smith Hospital to declare Munoz dead and remove her from life support by 5 p.m. Monday, WFAA-TV, Dallas, reported.
The ruling came after attorneys for husband Erick Munoz and the hospital jointly filed a document conceding the fetus was not viable "at the time of this hearing," the Dallas Morning News reported.
Marlise Munoz, 33, has been kept alive since suffering a pulmonary embolism just before Thanksgiving, when she was 14 weeks pregnant.
Hospital officials said Texas law forbids removing her from life support because she was pregnant.
The hospital had acknowledged Thursday Marlise Munoz was brain dead but Friday's filing is its first confirmation the fetus is not viable, the newspaper said.
The hospital has said it could not withdraw life support without causing "the death of an unborn child."
Erick Munoz is suing the hospital, saying it is not implementing the state law appropriately.
A Southern Methodist University associate law professor who helped draft the law in 1999 said lawmakers never considered whether it would apply to someone who is brain dead.
"It never would have occurred to us that anything in the statute applied to anyone who was dead," Thomas Mayo told the Fort Worth Star Telegram. "The statute was meant for making treatment decisions for patients with terminal or irreversible conditions."