Spinal anesthesia is well tolerated , it still is associated with considerable side effect ,most common being hypotension due to sympatholysis , is occurring in upto 75% of cases,potentially endangerous to both mother and fetus. Spinal block leads to sympatholysis ,may leads to vasodialation and consequentally cause maternal hypotension , which compromise uterine blood flow and fetal circulation and cause fetal hypoxia ,bradycardia and acidosis. Incidence of hypotension in genral population 25-75% and even higher in parturient due to physiological change in pregnancy that cause compression in inferior venae cava by hypertrophic uterus and also due to collateral venous plexus in epidural space , the physiological change in epidural space result in increase pressure of cerebrospinal fluid in lumbosacral area which result in cephalod spread of local anaesthestics these case rapid onset of sympatholysis due to increase sensitivity of nerve fiber to local anaesthetics during pregnancy . Higher sensitivity of nerve fiber towards local anaesthetics and aorto cavel compression of pregnant ueterus ,are rthe main reason for the increase incidence and higher level of hypotension in pregnant women as compare to non pregnant women, Pregnant women have increase sympathetic activity as compare to parasympathetic , then sympatholytic activity may leads to higher degree of vasodialatation ,consequntally decrease venous return , cardiac preload , bradycardia nausea and vomiting in mother The Duration of hypotension play importance role than its severity , hypotension <2 minute didn,t affect neurodevlopment outcome , whereas maternal hypotension lasting >4 minute neurodevlopment in first week of life and may persist through life long. A Number of measurement and treatment are use in clinicle practice in spinal anasthesia induce hypotension as – -Preloading and coloading with colloid -Compressing of lower limb with compression stocking or bandage -Administration of optimal dose of local anasthetics -left tilt positioning - adminastration of ionotrops and vessopressure, phenylephrine is preferred which associated with lower incidence of fetal acidemia ,nausea and vomiting Thus identification of multifactor of spinal anasthesia induce hypotension. Might help to prevent them dramatic consequnces in mother and fetus. Thus through this study we observe the effect of maternal BMI fetal and newborn weight on hypotension by observe 100 sample patient 12 month in pmssy building sgpgi lucknow. After ethical comettie approval and CTRI registration.