I thought I was going to die on a plane during depressurization once. My head literally felt like it was going to pop from my forehead and the pain was so immense I hunched over as to not cause panic in the aircraft.

It had happened a couple other times before this particular instance where the front of my head felt immense pressure during the planes decent. It also caused major headaches that lasted several days after the incident.

I looked it up after this event and made an immediate appointment with my doctor. Turns out some 10% of men can be affected by this where fluid builds up in your forehead "sinus pouches" I'll call them, and during the planes decent it will depressurize. During depressurization this fluid will push against your brain. You can see a similar action with a half filled waterbottle during this time. They implode a little bit. That's what was happening to my head.

My doctor prescribed me a nasal spray I need to take 30 minutes before take off to drain my sinus. It's worked ever since.

I suppose the airlines want that for liability reasons. But I'm curious of 'why' pregnant women need a doctor's note and not, say, folks with heart conditions then. Are there other groups that require some authority figure to give them medical permission to fly or do we only not trust pregnant women to listen to their doctors?

And adding to that: Depending on the flight you might be hours away from a suitable landing location with usually no medical personell or medical supplies beyond some band-aids available.

If something goes wrong, even unrelated to pressure, oxygen or cramped environment, you might be stuck up there for a very long time before you can get to a hospital.

The liability thing is definitely part of it but it ain't good news for anyone involved if that thing decides to pop out over the Pacific.