Hi! Ang baby's heartbeat ay usually na-detect na around 6-7 weeks using transvaginal ultrasound, kaya yun na talaga ang best time to do it if gusto mo makita agad, mas malinaw pa kaysa transabdominal ultrasound sa early weeks. One of my mum friends did hers at 6 weeks and nakita na niya agad yung flutter, super magical talaga! But honestly, check with your OB kasi bawat clinic has their own protocol, at gusto nilang sigurado na everything's progressing well bago mag-transv pa lang. Congratulations sa baby mo!