Honestly, depende sa OB mo and kung may specific concerns, but most of my mum friends got both, abdominal para makita ang baby's position and amniotic fluid, pelvic para sa cervix and placenta placement, kaya mas safe lang talaga. Better to ask your doctor kung bakit siya nag-request or kung pwede lang pelvic, pero usually pag third trimester na, gusto nila abdominal para complete ang picture bago ka magdeliver!