I've never flown while pregnant before. My DH and I are planning a trip to Puerto Rico in early January when I'll be 29 weeks. So far, I know to get up to walk every hour and half. I figure packing snacks would be good too. Any other pieces of advice to those who've traveled by plane, especially around this stage in pregnancy? I'm excited but a little nervous.

Thanks mommas!
Re: How to prep for plane travel planned at 29 weeks?
Try get an aisle seat near a bathroom.
Bring snacks and water!
Decide whether you will go through the X-ray scanner or get a pat down.
Bring a hoody or something to keep warm.
Bring a good supportive travel pillow.
Maybe purchase some flight socks.
That's all I can think of right now...
I can't imagine flying at 28-29 weeks. I had a business trip last week that required me to travel from the Midwest to the east coast, and my ankles were sooooooo swollen (its the only time I have ever had swelling). I think I would be miserable traveling long distances that late in my pregnancy.
I agree with PP about snacks, lots of water, and comfy pillows!
Good luck and have fun on your trips ladies! Even though I don't envy the travel time while pregnant, I do envy the vacations themselves! 
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Just hope it's a smooth flight so I can get up and love around
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I did calf raises and such and went to the bathroom for the walk every hour.
The only advice that hasn't been listed is that if you *look* really pregnant it might be a good idea to get a note from your doctor stating what week of pregnancy you are. Some airlines won't let you fly after 36 weeks, and I've heard of airlines being really weird about it.
I figure flying at 30 weeks having this do cent should be fine enough? Or should I ask for a note as well... at 21weeks today I am def showing so I imagine it's only going to get worse!
DS2 due 12/12/18
DH will have the aisle seat because he doesn't fit into planes very well (6'2") and he's an extremely nervous flyer (won't open the window shade or look out no matter what). He's just going to have to deal with me getting up and down a lot.
Better to know ahead of time and not get caught.
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DD2 - BFP 2/9/18 (EDD 10/19/18). "Grow baby grow!" DOB 10/24/18
BFP 11/16/20 (EDD 7/31/21). "Round 3 FIGHT!"
1.) buy the biggest bottle of water you can find before boarding and drink it all on the flight. If you have a connecting flight, grab another water or refill between legs. Flying is always dehydrating but I have found it to be more so while pregnant. Skip the sodas and juices (and pretzels!) on board and just stick with water during the flight. Take water every time it is offered to you by the crew too. Honestly, I never feel like I have to pee too much when I am flying, no matter how much water I have!
2.) bring some healthy snacks from home if possible - especially if you have flight connections because sometimes timing gets tight and you may not have time to eat (or find even a relatively healthy food option - much less one that's on the "foods allowed during pregnancy" list!). Some of my favorite snacks to bring are hydrating fruits and veggies like grapes, watermelon, carrots, and celery. Bananas and apples are usually easy to find in airports and so are yogurt, hummus, and tomato / basil / mozzarella sandwiches.
3.) absolutely get an aisle seat so you can get up whenever you want. Call the airline if you weren't able to get one when you booked and say your doctor recommended it.
4.) get up and walk up and down the aisle as often as you like. I usually end up doing a few "laps" every hour or so. Also, stand in the back of the plane and do stretches or a few exercises like calf raises. The crew never gives me any issues about doing this, though I only try stand in the back to stretch when there isn't a line waiting on the rest room. I haven't tried compression socks but haven't had any swelling issues so far.
5.) most people like to sit at the front of the plane, but I prefer to sit in the back for long flights. That way you can see the whole plane easily and know when there is a line for the rest room, so you can quickly scoot in when no one else is waiting. Otherwise you may end up standing in a line for a while, and sometimes the crew asks people to sit down as opposed to hovering in the aisles. Also, if you're up the front, you can't get to the back of the plane while the crew is in the aisle with the cart. If you're in the back, this doesn't really happen. Just my personal preference but I find it much easier to be in the back for long flights!
6.) keep your favorite chapstick and a small container of your favorite lotion or moisturizer handy. Not only is the air on board dry, but the soap and water in the restrooms seem to be really drying too. I try to take extra care to
moisturize my face before and after long flights (and sometimes during!).
7.) consider bringing a small hand sanitizer. I feel like I've become more of a germaphobe since becoming pregnant. Airports - yuck!
Bon voyage!
They help me at work. I spend a lot of time standing.