Oo, normal yan mama! Ang baby heartbeat sa first trimester ay usually around 110-160 bpm, kaya 173 is still within the okay range, babies' hearts beat faster than ours. Pero since this is your first time and gusto mo talaga maging sure, best pa rin to mention it sa OB mo sa next check-up, para for your peace of mind lang talaga, at least alam mo exactly what she thinks. Congratulations sa first pregnancy!