Ssecurity forces are to examine a suspect device found under a car in Co Tyrone last night.
The car was parked outside the woman's house in Greystone near Dungannon when the device was spotted, and a British army bomb squad was called to the scene.
Ms Michelle Gildernew, the Sinn Féin MP for Fermanagh-South Tyrone, said the woman, a Catholic, was seven months pregnant and was "very scared" by the discovery.
Ms Gildernew said she believed this was a loyalist assassination attempt.
"This is worrying stuff," she said. "There have been fears about loyalist death squads in the area targeting Catholics and I believe this has very sinister overtones."
The woman, who is in her 30s, was later found by police at a house some 10 miles away.
A PSNI spokesman said several hours elapsed between the time the device was first spotted and the time it was reported to them.
Additional reporting by PA