Gestational age-specific reference values of placental thickness in normal pregnant women.

The aim of this study was to determine the reference values of the placental thickness in 400 normal pregnant women during weeks 16-41 of gestation who were referred to the Mahdiyeh hospital during January 2014-February 2015. The placental thickness at the junction of the umbilical artery was measured using ultrasonography. Multivariable linear regression was used to model the mean placental thickness and assess associations with measured covariates, including gestational age (GA). Centiles for placental thickness distribution were estimated according to the modulus exponential-normal model. The mean and standard deviation of the age of the participants was 31.4 +/- 5.7 years. The Pearson correlation coefficient indicated a very strong positive linear correlation between GA and placental thickness (p r = 0.93). A nonlinear increase of placental thickness with estimated fetal weights was observed. GA-specific placental thicknesses for the 2.5th, 5th, 10th, 25th, 50th, 75th, 90th, 95th, and 97.5th percentiles of placental thickness were calculated. By making use of the provided nomogram in this study, neonatal outcomes associated with the placental thickness, such as Hemoglobin Bart's disease, can be diagnosed early to improve maternal and newborn health.