Close to term, but really at any time in pregnancy, you shouldn't be in some mode of transportation in which medical help is several hours or days away. At least on a USA road trip, there's a hospital available every couple of hours. But overnight camping and hiking trips would pose a problem should an emergency develop that required immediate assistance. The same goes for long flights over oceans—airlines aren't equipped to do anything useful in the case of complications of pregnancy. Cruises are worrisome, also.
When you travel, know your due date and your blood type, the two most important things a new doctor would want to know about you.
BOTTOM LINE: Keep civilization available. Know your due date and blood type.
Use them. The most common reason for fetal death in a car accident is maternal death because of not using seatbelts.
BOTTOM LINE: Use seatbelts, without exception.
The big companies have spent a lot of money on FDA approval and the studies to pursue it, so you can't go wrong staying with a big company's prescription prenatal vitamin. Folic acid is becoming a rising star in pregnancy.
Beware of do-it-yourself multivitamin concoctions that are designed by salespersons at health food stores. They can't do a better job than the big companies, and sometimes too much of a vitamin can be harmful.
BOTTOM LINE: Use the prescription prenatal vitamins; don't use any other herbal or do-it-yourself concoctions, unless prescribed by your obstetrician.