Placental thickness estimation by ultrasonography and its correlation with gestational age in normal pregnancies in late 2nd and 3rd trimester

Abstract

Introduction: At present, the most effective way to date pregnancy is by the use of ultrasound. Placental thickness can be used
as a new parameter to estimate gestational age. Aim: The aim is to study placental thickness as a parameter for estimation of the
gestational age of the fetus and assess the placental growth pattern with the advancement of gestational age. Methods: A total of
298 antenatal women between 18th week and 40th week of gestation (GA) by last menstrual period (LMP) were included who were
sure of their LMP. Pregnancies with a history of medical disease, fetal anomalies, placental anomalies, and poly/oligohydramnios
were excluded from the study. Pregnancies with poor visualization of placenta were also excluded. Placental thickness was measured
at the level of insertion of umbilical cord, and gestational age was calculated by LMP. Correlation of mean placental thickness with
GA age by ultrasonography was studied. Results and Discussion: We observed that mean placental thickness gradually increased
from 18.7 mm at 18th week to 30.5 mm at 40th week of GA. From 18th to 32th weeks of GA, placental thickness (mm) almost matchs
the gestational age (weeks), and thereafter, placental thickness slightly decreases and remains nearly constant till 40th week of GA
with an average value of 31 mm. Findings were consistent with the previous studies where several authors have found that mean
placental thickness (mm) increases with gestational age and coincides almost with gestational age (weeks). Conclusion: Placental
thickness measurement can be an important parameter for estimating gestational age.