Hai! Baby hardening (Braxton Hicks) tu memang rasa mcm perut jadi tegang dan keras suddenly, macam otot tu kuncup je lepas tu relax balik, biasa between 6-9 months tapi some of us felt it earlier or later. Rasa dia bukan sakit sih, just uncomfortable tightening, and boleh jadi anywhere depende position baby tu, bukan specific ke sebelah kiri je, tapi kalau tu rasa sakit or bleeding or frequent, definitely go see your doctor kay!