Ultrasonographic Evaluation of Placental Thickness in Normal Singleton Pregnancies for Estimation of Gestation Age

Abstract

Background: Use of ultrasonography is the most effective method to estimate the gestational age. Placental thickness can be used as a new parameter to estimate the gestational age of the fetus and to assess the growth pattern of the placenta with advancing gestational age. Methods: This was a prospective cross sectional study consisting 150 normal antenatal women who were assessed clinically at the Department of Obstetrics and Gyaenocology and referred to the Department of Radiology, College of Medical Sciences, Bharatpur for ultrasonography. Antenatal women of all gestational ages from 11 weeks to 40 weeks of gestation with normal singleton pregnancies were included in the study. Placental thickness value, in mm, was calculated by averaging the three best measurements for each case. Relationship of placental thickness (in mm), measured at the level of insertion of umbilical cord with advancing gestational age in weeks was studied. Correlation of mean placental thickness with gestational age from 11 weeks to 40 weeks was calculated. Results: It was observed that the placental thickness gradually increased from approximately 11 mm at 11 weeks to 38.33 mm at 40 weeks of gestation. From 11 to 34 weeks of gestation, the placental thickness (in mm) almost matched the gestational age in weeks, thereafter from 35 to 40 weeks; the placental thickness was lower by 1 to 2 mm. Conclusion: The relationship between the placental thickness and gestational age was linear and direct. Placental thickness (in mm) measurement can be an important additional parameter for estimating gestational age along with other parameters especially from 11 to 34 weeks of gestation.