Background: Prolonged gestation complicates 5% to 10% of all pregnancies and confers increased risk to both the fetus and mother. In the west about 18% of all singleton pregnancies persist > 41 weeks, 10%, >42 weeks and 4% (range, 2% to 7%) > 43 weeks without any obstetric intervention. The risks for prolonged and post-term pregnancy include obesity, nulliparity, maternal age >30 years. Racial and ethnic differences have also been cited to be the reasons for higher risk of prolonged and post-term pregnancy. Methods: A prospective study was carried out at Department of Obstetrics and Gynaecology, Gauhati Medical College & Hospital, Guwahati, Assam. 300 patients were selected and divided into three groups and were followed up with Doppler and MBPP till the delivery. Data so collected was subjected to Statistical analysis. Results: Majority of women enrolled in the study were aged around 25 years, multigravida (58%) and the study and control groups were matched demographically. The Doppler & modified biophysical profile was recorded in study and control group. Rate of caesarean delivery in spontaneous & induced, Baby NICU admission &mortality. Conclusions: This study had showed that its use can predict adverse perinatal outcome in low risk pregnancy in prediction of asphyxia. Hence our study recommends use of combimed Cerebroplacental ratio & MBPP has better sensitivity in postdated pregnancy to predict adverse perinatal outcome.