Stress is always a concern, though. She should allow plenty of rest periods, plan frequent trips to the bathroom, and stretch her legs a few times every hour. If she begins to experience any low back pain, cramping or any spotting, she should seek out a care provider in the area and not try to make it back home. Even in confined areas, exercise is important. It is a good idea to do simple isometric muscle strengthening exercises while traveling by car or airplane.
Pelvic rock is an excellent one for pregnant women.
When your daughter is about 26 weeks, approximately at the beginning of her 3rd trimester, she will probably have an exam to see if she is having any early changes that might indicate risk of preterm labor. If she has no signs and she is not experiencing any contractions or back aches, she can probably continue to fly. She should carry a copy of her most recent prenatal record, just in case she needs to consult another care provider or if she does go into labor in a strange city. The old stand-by prescription is true in pregnancy also. Sometimes, dehydration is enough to cause uterine contractions.