For the occasional traveler with an uncomplicated pregnancy, flying is not known to be associated with any significant risks. After the 36th week of pregnancy, many obstetricians restrict flying because the patient may not be able to get immediate care if she should go into labor.

Flying as a professional occupation while pregnant is a more complex issue, involving fetal risks, maternal risks and aircrew performance.

The maternal risks include decreased balance, decreased motion tolerance, decreased g-tolerance, gas compression/recompression effects. During the second and third trimester, placental abruption caused by the shearing force of inadvertently falling or striking the abdomen violently is a relatively common occurrence.

Fetal risks include exposure to noise, heat, chemicals, organic solvents, and low-frequency, whole-body vibration.

For these reasons, there is general agreement to restrict pregnant aircrewman from participating in high-performance aircraft flights. There is less agreement in the area of helicopters and multiengine, fixed-wing aircraft.

Whether to allow a pregnant aircrewmember to continue her flight duties should be individualized, after considering the stage of pregnancy, the presence or absence of risk factors for her pregnancy or her flight crew performance, her company's rules, and the degree of exposure to potentially harmful stressors in the aviation environment.