if there is no concern, 1 beses ang TVS during 1st trimester.
ako, 3× na TVS during 1st trimester.
1st- first prenatal check up to determine AOG.
2nd- to check reason of cramping.
3rd- to check if there are no more contractions.
after that, ang next ultrasound ko ay CAS na, during 2nd trimester.
after that, next ultrasound ay BPS during 3rd trimester.