Some women get such strong nesting instincts during pregnancy that they're happy to stay home, clean house and redecorate. Others feel the urge to see the world. After all, especially if it's a first child, this may be the last chance for awhile to take a trip unencumbered by diapers, wipes and a stroller. If you fall into the second group, the good news is that most obstetricians say there's no reason most women can't travel during a healthy pregnancy. But there are some guidelines that can help make any trip -- work or pleasure -- footloose and fancy-free.

Timing
Assuming you have complete freedom to schedule your trip -- meaning it's not for a crucial business meeting or a required family function -- doctors say the best time for a pregnant woman to travel is during the second trimester (the 13th to 28th weeks). The fatigue, nausea and increased miscarriage risk of the first three months have ended. And the heaviness, fatigue and risk of premature labor of the last three months haven't yet begun.

Transportation
If you're traveling by air, the biggest concern is the dangerous blood clots that can form in your legs after hours of inactivity. While all travelers are at increased risk, the danger is greater for pregnant women. Try to sit in an aisle or bulkhead seat that will allow you to stretch and move your legs as much as possible. And get up from your seat frequently -- at least every two hours -- to walk around.

Dehydration is another potential problem on long flights, since the air on planes is extremely dry. Bring a big bottle of water along or make frequent requests to the flight attendants. "If you're not getting up to go to the bathroom every two hours, then you're not drinking enough," says Sharon Phelan, M.D., professor of obstetrics and gynecology at the University of New Mexico in Albequerque.

Lately, there's been some concern about the radiation exposure from the sun that air travelers face. While this may be a problem for very frequent travelers (including pilots, navigators and flight attendants), obstetricians say that one or two trips during pregnancy isn't a concern.

If you're traveling on the ground -- via train or car -- be sure to get out of your seat or stop the car for a walk or other exercise every couple of hours. Long bus trips should probably be avoided, since it's difficult to leave your seat. Always bring along a water bottle to keep yourself hydrated.

Pregnant women traveling by boat may be more likely to experience the nausea of seasickness. If you're determined to take a cruise, doctors say that most over-the-counter anti-motion sickness medications (such as Dramamine) are safe for pregnant women. But, as always, check with your obstetrician before assuming anything is safe for you.

General Rules

• It's a good idea to see your obstetrician and get his or her okay before going anywhere.
• If you're taking commercial transportation -- especially planes -- ask your doctor at this checkup to write a note stating that he/she has recently examined you and considers it safe for you to travel. The note should also state your due date. Some airlines will refuse to board a pregnant woman who looks as if she's close to her delivery date. If you're carrying large, this note may help overcome an airline's reluctance.
• Don't plan to be far from competent medical help -- especially in your last trimester. It's very different dealing with a pregnancy emergency in Katmandu versus California. No matter how healthy you are, pregnancy is not the smartest time to plan an exotic trip, which might involve vaccinations, anti-malaria drugs or unsafe food and water. "I had a patient who was pregnant with twins ask me if it would be okay for her to go to Nepal in her 28th week. I said, 'No!' She could do what she wanted, of course, but she wanted my permission, and I wasn't going to give it," says Dr. Phelan.
• If possible, know the name and address of the closest hospital, in case you need to visit the emergency room.
• Finally, just because you're away from home and work responsibilities, never forget you're pregnant. No matter where you are, it's still important to follow a healthy diet, drink enough fluids, leave time for relaxation, and avoid activities (such as skiing, scuba diving, or saunas) that might be dangerous for you and your unborn child.