The second trimester is the safest time for travelling, because the pregnant 
woman feels generally most at ease and the risk of spontaneous abortion and 
pre-term labour is very low. Possible risks must be discussed with the 
obstetrician before travelling. If the pregnancy is uncomplicated most airlines 
allow flying up to the 36th (domestic flights) and 35th (international flights) 
week of gestation. Unless the fetal oxygen supply is already impaired at ground 
level due to an underlying disease, flying does not pose a risk of fetal 
hypoxia. Radiation exposure during a long distant flight is low compared to the 
average annual exposure dosage, but the risk of thrombosis is increased. 
Altitudes up to 2,500 m pose no problem. Sufficient time to acclimatize must be 
taken when travelling to high altitudes and exercise kept to a minimum. Scuba 
diving is contraindicated. Since only a few drugs are completely safe during 
pregnancy a thorough risk/benefit evaluation is mandatory. Treatment of 
infections can be considerably complicated, but any necessary treatment should 
not be withheld because of the fear of potential fetal injury. Good knowledge of 
local medical resources is essential before travelling. Several personal 
protective measures minimize the risk of infection: food and water precautions, 
protection from insect bites and avoidance of crowds, unsafe sex and, if need 
be, freshwater. Many vaccinations are recommended for travellers. However, live 
vaccines are contraindicated in pregnant women because of theoretical 
considerations. Exceptionally a yellow fever vaccination may be given after the 
first trimester. Killed, inactivated or polysaccharide vaccines can be given 
after the first trimester after a thorough risk/benefit evaluation. Because of 
the potentially devastating effect of malaria to the mother and the child, 
travelling to endemic malaria regions should be avoided. If the risk of 
infection is high chemoprophylaxis with mefloquine is indicated. In low-risk 
countries mefloquine, in South-East-Asia artemisinin derivatives should be given 
as stand-by treatment.