Yes, you can fly for 13 hours while pregnant, provided you have a straightforward, uncomplicated pregnancy and have consulted your doctor or midwife. Most airlines allow pregnant travelers to fly until their 36th or 37th week (or 32nd week for twins), though many require a medical certificate after 28 weeks confirming your due date and health status. The primary concern with ultra-long-haul flights is the increased risk of Deep Vein Thrombosis (DVT), as pregnancy already naturally increases blood-clotting factors. To mitigate this during a 13-hour journey, you should wear graduated compression stockings, stay hydrated by drinking plenty of water, and walk around the cabin at least once every hour. Additionally, ensure you have comprehensive travel insurance that covers pregnancy-related complications and research the medical facilities at your destination. Avoid flying if you have severe anemia, recent vaginal bleeding, or a history of premature labor, as being in the air for 13 hours makes emergency medical diversion difficult.