Development of a nomogram to evaluate the usefulness of sonographic measurement of placental thickness for the estimation of fetal gestational age

Abstract

Background: An accurate assessment of gestational age (GA) and evaluation of fetal growth is fundamental to prenatal care.  Aim: To evaluate placental thickness (PT) as an indicator of GA. Subjects and Methods: A prospective study was carried out on 300 antenatal patients with known last menstrual period (LMP), 100 each in first, second, and third trimester, respectively, with GA more than 10 weeks till term in a study period of one year. Patients with GA more than 20 weeks detected with pregnancy‑induced hypertension (PIH) and/or diabetes mellitus (DM) and/or intrauterine growth retardation (IUGR) and/or hydrops fetalis and/or congenital malformation were excluded from the study. Twin pregnancy of any gestation was excluded from the study. The PT was measured at the level of insertion of the cord and the values thus measured in millimeters was correlated with GA as ascertained vis a vis the LMP. GA and PT were represented as mean and standard deviation. Correlation between them was evaluated using Pearson’s product moment correlation coefficient. Results: The study showed a positive correlation between GA and PT. PT in millimeter accurately matched the GA in weeks from 14 to 21 weeks of gestation after which it was seen to be lesser than GA by 1-4 mm. Conclusions: PT promises to be an accurate parameter for estimating fetal GA in singleton pregnancies. Keywords: Fetal Gestational age, nomogram, placental thickness