Grisel Barranco's family says she is four months pregnant.
Her husband Jose Quintanilla, her mother Jimena Barranco, and her 2-year-old son Sebastian were all killed in the crash, which shut down Highway 288 in Pearland on Sunday evening.
Houston police say Larry Williams, 37, was speeding down Highway 288 when he veered off the exit lane and into a main lane, and slammed into the Quintanilla family's small car.
Williams has been charged with possessing a small amount of marijuana at the time of the crash, but police say Williams doesn't appear to have been intoxicated while driving.
Williams is out of jail on a $5,000 bond, but police say more charges could be filed against him as the investigation continues.
Report a typo to the ABC13 staff