I had threatened miscarriage at ~12 wks in my first pregnancy. i am now 4 wks pregnant & will fly long distance in 2 wks (16hrs each way) is it risky?

No, but be careful: The flight itself is not a risk to your pregnancy. However, the typical process in long flights involves you sitting for prolonged periods of time and possibly getting dehydrated. Make sure you drink plenty of water and try to get up to walk every couple hours to promote good circulation through your legs and prevent blood clot formation.