Plot hole: When the armored guy is propelled under the tanker trailer, his backpack explodes. That blast can not have been large enough to lift the entire trailer through the air. The trailer never explodes itself, and if it did, the tank itself would have torn apart and the frame beneath would have stayed on the ground, pushed down by that blast above. (Oh, and there's no such "safety feature" that is intended to launch a trailer in the air in case of an accident.) (00:05:00)
Plot hole: When Riggs, Murtaugh, Lorna and the others are tied up and lying on the floor of the burning house, they can't stop coughing. However, the bad guys (who are also in the burning house) are just standing around laughing, wouldn't you think that they would be inhaling smoke also?
Chosen answer: She could have taken a taxi or an ambulance, or even driven herself. A neighbor or friend could have taken her who didn't stay after she was admitted. She might have already been at the hospital for any number of reasons - doctor's appointment, already admitted for bed rest prior to labor, etc. etc. etc.
Myridon