Uy, alam mo yan changes pa talaga kaya don't stress yourself too much ngayon! At 13 weeks pa lang siya, and placenta is still migrating pa, marami sa amin na may anterior placenta early on tapos nag-move na by second or third trimester, so very possible na babago pa. The good news is your baby's heartbeat is strong at 158 bpm, which is perfect, so that's what matters most right now! Just schedule your next ultrasound kasi kailangan mo ng peace of mind, and let your doctor explain kung ano exactly ang risk level mo, sometimes the phrasing gets scary but your OB can break down kung ano talaga ang concerns based on where exactly your placenta is. Praying it moves for you, mama!