Flying while pregnant: cut-off date calculator

How the cut-off date is calculated

A due date is 40 weeks 0 days of pregnancy, so the date on which you reach w weeks and d days is:

due date − (280 − (7w + d)) days

Airlines phrase the same rule two ways. “The end of the 36th week” means 36 weeks and 6 days. “You cannot travel from the 37th week” means from 37 weeks and 0 days, which is the day after. Both produce the same last permitted travel date, and the tool converts either into a single date.

Two counting conventions to watch. Qatar Airways defines “29 weeks” as beginning at 28 weeks and 7 days. Turkish Airlines counts in days rather than weeks — its certificate window is 190 to 244 days of pregnancy. Lufthansa anchors to the expected date of delivery rather than to gestational weeks, which makes its two published limits land six days apart; this tool uses the earlier of the two.

Airline policies, from each carrier's own published page

The patterns worth knowing

• Multiples are cut off roughly four weeks earlier almost everywhere, because labour is more likely to start earlier.
• Only Qantas and Air New Zealand key the limit to flight duration — and the difference is four whole weeks, at a four-hour boundary.
• Only Aer Lingus splits by route rather than duration: week 36 within Europe, week 34 transatlantic.
• US carriers mostly do not use gestational weeks at all. They key to proximity to the due date. American wants a certificate within 4 weeks of the due date; JetBlue bars travel within 7 days of delivery; Southwest merely advises against the 38th week onwards; Delta publishes nothing.
• The return leg counts. easyJet states explicitly that the return must also be completed before the limit. Booking the outbound against the cut-off and forgetting the flight home is the most expensive mistake people make.
• Connections take the strictest rule. JetBlue warns that codeshare and interline partners may be stricter than JetBlue itself.

Three airlines are deliberately missing

British Airways, Jet2 and United are not included because their published pages could not be read: britishairways.com serves a holding page to anything that is not a browser, jet2.com returns a server error at its edge, and united.com serves an application shell with the content behind a blocked API. Rather than print a figure it has not verified from the carrier's own page, this tool names them and sends you to their sites.

The medical guidance, which is a separate thing entirely

Airline limits are commercial, not clinical. RCOG's Scientific Impact Paper No. 1 states it directly: “The main concern restricting the airlines from accepting pregnant women as passengers relates to the risk of labour developing, which may disrupt or divert the flight and the lack of appropriate care providers and facilities to manage labour or any obstetric complication in flight.” And: “Even at advanced gestation, there is no significant risk associated directly with flying.” The cut-off is about where the aeroplane would have to land.

RCOG's patient information adds: “Occasional air travel during pregnancy is not harmful for you or your baby as long as you are having an uncomplicated pregnancy”, and “there is no evidence that flying will cause miscarriage, early labour or your waters to break.” It advises travelling before 37 weeks with one baby and before 32 weeks with an uncomplicated twin pregnancy, because from then labour could start at any time.

ACOG puts the best window at 14 to 28 weeks: “During these weeks, your energy has returned, morning sickness is improved or gone, and you are still able to get around easily.” It notes that most airlines allow flying within the United States until about 36 weeks and that international cut-offs may be earlier.

Blood clots

This is the risk actually worth managing, and it scales with flight length. ACOG: “Research shows that any type of travel lasting 4 hours or more — whether by car, train, bus, or plane — doubles the risk of DVT. Being pregnant is an extra risk factor for DVT.” RCOG quantifies it: prolonged air travel results in a roughly three-fold increase in the absolute incidence of venous thromboembolism, with an 18% higher risk for each 2-hour increase in flight duration — though the absolute rate stays low, at about 1 in 4,600 flights in the month following a 4-hour flight.

Graduated elastic compression stockings reduce the risk of asymptomatic DVT with a relative risk of 0.10 (95% CI 0.04–0.25). They must be fitted for you: RCOG notes they are different from standard flight socks and that your midwife or doctor needs to provide the correct size and type. Low-dose aspirin does not appear to reduce the risk. On a flight under four hours RCOG says it is unlikely you will need any special measures; on anything longer, take an aisle seat, walk, do in-seat exercises every 30 minutes, drink water and cut the caffeine.

Seatbelts, radiation and scanners

Wear the belt at all times; turbulence arrives without warning. RCOG: fasten it “reasonably tightly across the top of your thighs and then under your bump”. ACOG says the same — low on the hip bones, below your belly. On radiation, RCOG: “Anyone who flies is exposed to a slight increase in radiation. Occasional flights are not considered to present a risk to you or your baby.” Security scanners are “not considered to be a risk” either, and ACOG agrees exposure is not a concern for occasional travel. Frequent flying is a different calculation: RCOG's scientific paper notes fetal dose can exceed a recommended 1 mSv limit after roughly ten return trips between Toronto and Frankfurt.

Insurance and when not to fly

RCOG notes it may be more difficult to get travel insurance after 37 weeks. ACOG advises avoiding flying if you have a medical or pregnancy condition that could be made worse by flying or could require emergency care, and notes that most common pregnancy emergencies happen in the first and third trimesters.