Daisygirl- I'm a flight attendant for a major airline and only fly international for work. There is NOTHING different with how you became pregnant and air travel. Personally I stopped flying at 22w but I was working and on my feet for over 8hrs at a time..not sitting as a passenger.
These are the risks I see for traveling while pregnant.
1. I see many moms get very dehydrated, they don't drink NEARLY enough for long flights. India is one of the longest you can go on. You need to drink at least 4L of water on a flight that long. I'm not even joking...especially when you are drinking for two. You can't depend on your flight attendants to provide you with that much water. The plane just doesn't hold it. You have to bring your own. Buy it after you clear security. It will cost more but you CAN take it on the plane. If you buy it before security they will take it.
2. Many moms...and people in general do not get up enough and are at risk for DVT. Deep vein thrombosis, or blood clots in your legs. You legs will cramp and it can be deadly. Get up and walk around. You'll need to after drinking that much water any how.

You can do stretches in your seat to work out your legs and ankles. Do not go back to the galley and act like it's your personal yoga studio. As long as a service is not going on you can stretch in the aisle or while waiting in line for the bathroom.
3. There are many shots that are advised for you to get for travel to India. You can not get these shots while pregnant. My Dr vetoed travel to India while I was pregnant. Fine with me. It's too easy to pick up a bug and if you don't really need to go I suggest you wait.
All in all, if you have to go to India just drink plenty of water and bring your own healthy snacks. There is never enough food on a flight unless you are in first class and there is never enough personal water. BRING YOUR OWN! Don't ever depend on someone else to know what you want, like or need. Water will also help you fight jet lag.
Safe travels and if you have any questions please let me know.