For pregnant humans, airplane restrictions are pretty straight-forward — a person can fly until they're about 36 weeks pregnant, as long as their doctor approves — and in most cases a lack of comfort during the flight is the biggest issue. For dogs, however, pregnancy and air travel rules are a bit more complicated. Whether or not you can fly with a dog that's pregnant depends on how far along your dog is in her pregnancy, and what kind of health she's in. Travel restrictions and regulations for pregnant dogs are merely suggestions by most vets, not airlines, and they are in place to ensure the health of both the mom and the babies since both are more vulnerable in flight. As you can imagine, pup travel is stressful enough for a healthy, happy dog that's not currently carrying a litter of pups.
An important factor to consider when accessing whether a pregnant dog should fly is the dog's emotional reactions to stressful things like travel. If your pup is an anxious traveler and gets easily overwhelmed or ill when outside of their comfort zone, air travel might not be a safe option for you two, if avoidable. Because dog pregnancy is so different than human pregnancy, the rules are quite different, too. Dogs are pregnant for just about two months (63 days) and unlike human pregnancies, the first three weeks are incredibly delicate. The general guideline, according to Vetinfo, that pregnant dogs should not travel at all during those first three weeks of pregnancy, or during the last two weeks of pregnancy because it can induce early labor. For any travel during the time between these two stages, ensure your dog is in a stress-free environment, and is as comfortable as possible during the journey. You can also have your vet assess your pup's health to see if they will issue a pet certificate that will enable the pup to fly.
Though most airlines don't have their own rules and regulations regarding pregnant dogs, the general rules for traveling with dogs apply: your pup must be approved by a vet to fly with a health certificate, and it must fit in a carrier bag that can be placed under the seat in front of you. While this technically means that a pregnant dog that fits these requirements can fly anywhere with you, it's worth remembering that traveling is still stressful for a pup, and that a dog's pregnancy needs to be monitored closely. The longer you are up in the air and away from a vet, the more that's at risk.
So, while it's ideal to avoid traveling with a pregnant dog if you can, it's technically allowed by airlines if you are able to get a vets note, the dog is small enough to fit in a cabin-approved carrier bag, and you're able to do whatever it takes to make sure that your pup feels cozy and calm in flight. And remember: if you're traveling somewhere new, make a list of local vets and emergency animal hospitals nearby, just in case.