Just got back from Switzerland and I was 18weeks when I went over. Keep yourself hydrated throughout the flight, stretch out your legs and ankles every now and then. I heard compression socks helps too but I had no time to get them so I walked up and down the aisle to get the flow flowing. Keep yourself and baby warm when it's cold :) heat tech from uniqlo is goood. Have a lovely honeymoon!!
As long as you get safe to travel from your dr, it’s fine. Research the hospital/emergency location at the place you are staying for in case of emergency. Bring compression socks and try to walk around during the long flight. Bring some medicine for nausea during flight.