Check your airlines guidance, check with travel insurance if pregnancy needs to be declared. If long haul flight get some DVT socks and ensure you walk around and stretch at frequent intervals. Ensure there are no issues with the destination you are planning to travel to (we checked with our midwife). The FTF will depend on the airline, some just require you to have it with you and show it, others require it to be logged with them beforehand.
You only need it after 28 weeks https://www.nhs.uk/pregnancy/keeping-well/travelling/
We changed our plans entirely because of Zika and my being pregnant a few weeks ago. The travel nurse advised me to stay away from countries with zika. Apart from that, our airline needed the FTF form and if you do any tours, I guess they need it too