International travel should be avoided by pregnant women with underlying medical conditions, such as diabetes or high blood pressure, or a history of complications during previous pregnancies, such as miscarriage or premature labor.

For pregnant women in good health, the second trimester (14/26 weeks) is probably the safest time to go abroad and the third trimester the least safe, since it's far better not to have to deliver in a foreign country.

Yellow fever vaccine, which consists of live virus, should not in general be given to pregnant women. Unless absolutely necessary, pregnant women should not travel to areas where yellow fever occurs, which includes most of equatorial Africa and many parts of South America. If travel to these areas is unavoidable, yellow fever vaccine may be considered if the benefits of vaccination appears to outweigh the risks.

In general, pregnant women should avoid traveling to areas where malaria transmission occurs. Malaria may cause life-threatening illness in both the mother and the unborn child. None of the currently available prophylactic medications is 100% effective. If travel to malarious areas is unavoidable, insect protection measures must be strictly followed at all times. The recommendations for DEET-containing insect repellents are the same for pregnant women as for other adults. Of the currently available drugs for malaria prophylaxis, chloroquine has the best safety record in pregnancy, but has lost its usefulness in many parts of the world. Mefloquine (Lariam) may be given if necessary in the second and third trimesters, but should be avoided in the first trimester. There are no data regarding the safety of atovaquone/proguanil (Malarone) during pregnancy, so the drug should be avoided pending further information. Doxycycline may interfere with fetal bone development and should not be given during pregnancy

Strict attention to food and water precautions is especially important for the pregnant traveler because some infections, such as listeriosis, have grave consequences for the developing fetus. Additionally, many of the medications used to treat travelers’ diarrhea may not be given during pregnancy. Quinolone antibiotics, such as ciprofloxacin (Cipro) and levofloxacin (Levaquin), should not be given because of concern they might interfere with fetal joint development. Data are limited concerning trimethoprim-sulfamethoxazole, but the drug should probably be avoided during pregnancy, especially the first trimester. Options for treating travelers’ diarrhea in pregnant women include azithromycin and third-generation cephalosporins. For symptomatic relief, the combination of kaolin and pectin (Kaopectate; Donnagel) appears to be safe, but loperamide (Imodium) should be used only when necessary. Adequate fluid intake is essential.

Iodine tablets should not be used for more than a few weeks during pregnancy, due to risk of congenital goiter. Bismuth compounds, such as Pepto-Bismol, should not be taken during pregnancy.

Vaccines which should not be given during pregnancy:

• Measles-mumps-rubella
• Varicella
• Yellow fever (may be considered if travel to high-risk area is unavoidable)

Vaccines for which safety data during pregnancy are not available:

• Hepatitis A (no data, but risk in pregnancy thought to be extremely low)
• Typhoid (Typhim Vi may be safest, since inactivated)
• Japanese encephalitis (avoid travel to high-risk areas)

Vaccines which may be administered during pregnancy if indicated (avoid immunization during first trimester):

• Hepatitis B
• Rabies (human diploid cell)
• Inactivated polio
• Meningococcal
• Tetanus-diphtheria
• Influenza

For further information, see Planning for a Healthy Pregnancy and Traveling While Pregnant on the CDC website and Pregnancy and travel from the U.K. Department of Health.

Other resources:

Baby and Pregnancy.co.uk