Travel considered long-term (more than 4 hours) and not exclusively by air, is a risk factor for venous thrombosis. They are related to the airplane trip if it happens in the 8 weeks after.

Travel over 4 hours
“It is not advisable to travel by plane before the 37th week with a single pregnancy and before week 32 with a twin pregnancy.”
- General measures indicated in every pregnant woman.
- Abundant intake of liquids (water).
- Avoid alcohol and caffeine.
- Intermittent wandering through the corridors of the plane.
- Perform periodic series of contraction of twins during the trip.
- Stockings/compression sock below the knee 15-30mm Hg.
- Evaluate to associate prophylactic LMWH guidelines 6-12 h before the flight until 1-3 days after the flight, in high-risk women with ETV (history of thrombosis, SAF) and other risk factors such as morbid obesity and nephrotic syndrome.
S.C. Cannegieter, F.R. Rosendaal . Thrombosis Research 131, Suppl. 1 (2013) S55–S58.
Royal College of Obstetricians and Gynaecologists.Air travel and pregnancy 2015.