Aim: This study aimed to establish a relationship between placental thickness and biparietal diameter by real time ultrasound for estimation of gestational age of fetus. Materials and Methods: This  study  consists  of  100  pregnant  females, between  13th    to  39th   weeks gestation  with  their  age  ranging  from  18 -35 years,  attending   antenatal  clinic  at  the department  of  Obstetrics  and  gynecology, Pt..J.N.M. Medical College and Dr. B.R. Ambedkar Memorial Hospital Raipur (C.G.) from October 2008 to august 2009.  Who were sure for the last menstrual period and fulfilling all criteria for selection of cases.USG was done for estimating   fetal age by biparietal diameter (BPD), and placental thickness (PT). BPD was measured from the outer surface of skull table of one side to the inner margin of skull table on opposite side.  PT  was  measured  perpendicular  to  the  basal  and  chorionic  plates, in the  mid  portion  of  the  placenta  at  the  level  of  insertion  of  umbilical  cord. Results: It was observed that the coefficient of correlation (r) between PT and BPD being at 26-30 weeks r = .988 ( p = .002), and at 31-35 weeks  r = .963 ( p = .009) which is statistically significant but at more than >35 weeks it become non significant. Conclusion: The study concluded a fairly linear relationship between PT and BPD and it provide accurate parameter for estimating fetal gestational age especially in the late mid trimester and early third trimester, where the exact duration of pregnancy is not known.

Keywords: Biparietal Diameter; Placental Thickness;  Fetal Growth; Gestational Age.