Hypotension is a common complication, subsequently spinal anaesthesia in lower segment caesarean section, which can cause adverse maternal & foetal outcomes. A new decisive research area in obstetric anaesthesia is prevention & early treatment of spinal hypotension to improve maternal & foetal outcomes. A novel parameter, Perfusion index (PI) is tried during sub arachnoid block for predicting hypotension in lower segment caesarean section (LSCS). In this study, 60 parturient belonging to ASA status 1 or 2 with apparent pregnancies scheduled for elective LSCS received spinal anaesthesia with 2ml of 0.5% heavy bupivacaine by using an orange (25G) Quincke needle at L3-L4 or L4-L5 interspinous space. Haemodynamics & perfusion index were recorded at regular intervals. Baseline perfusion index was correlated with degree of hypotension by using Receiver Operative Characteristic curve. Baseline perfusion index & other parameters were correlate by Karl Pearson correlation method. : In our study 34.5% incidence of hypotension among study theme & momentous correlation between fall in systolic blood pressure from baseline & baseline perfusion index (r = 0.436; P < 0.05). The optimal utmost point for perfusion index was found to be 3.5 with a sensitivity of 37% & specificity of 97%. A higher incidence of hypotension was found in Parturient having baseline perfusion index more than 3.5 following sub arachnoid block in elective LSCS.