According to the American College of Obstetricians and Gynecologists, occasional air travel in pregnancy is considered safe, and there are no data to show that air travel adversely affects pregnancy outcomes for occasional travelers. Most airlines allow women to fly up to the 36th week of gestation. Women who have high-risk pregnancies and are at risk for preterm labor or who may require emergency care should avoid air travel. It is generally recommended that pregnant women traveling by air take precaution to decrease their risk of developing blood clots (thrombi) in the extremities. The use of support stockings, frequent ambulation, and remaining well hydrated can help reduce the risks of developing a blood clot in the legs during long flights.