You may not want to travel abroad during your pregnancy. The trip will be long and you may be far from your doctor. But if you must travel out of the country, be prepared. Talk to your doctor well in advance.
The Centers for Disease Control and Prevention is a great resource for travelers. You can find out what immunizations you might need in specific countries, as well as safe vaccines for pregnant women.
To avoid traveler's diarrhea -- especially in Third World countries -- avoid drinking the water. If you're sure of the quality of bottled water, drink that and use it for everything, even brushing your teeth. Local brands of bottled water may not be safe. If there is any doubt, use only water that has been boiled for at least one minute. Don't consume drinks with ice made from water that hasn't been boiled. Canned juices and soft drinks may be a good alternative. Eat fresh fruits and vegetables only if they've been cooked or you can peel them. Of course, make sure meat and fish are thoroughly cooked. If you do get diarrhea, seek medical help. Find out in advance what remedies work well for pregnant women.
You never know what might happen, so buying travel insurance is a good idea in case you have to cancel. Also, make sure your medical insurance policy would cover both you and the baby while you're out of the country. If not, buy travel medical insurance before you go.
Know how to get in touch with a reputable doctor at your destination. The International Association for Medical Assistance to Travelers (IAMAT) has a directory of physicians from around the world. Because there can be no room for ambiguity when you get sick far from home, take a basic language dictionary with you on your trip.
However and wherever you travel, bon voyage. Read on for lots more information.