Correlation of placental thickness with gestational age in second and third trimester using ultrasonography

Background The accuracy of currently established parameters in estimating gestational age decreases as pregnancy advances. With advancing gestational age, there is an expected linear increase in placental thickness. Placental thickness may thus be used to reliably predict gestational age, especially in later stages.Aim Our study aimed to determine the relationship between placental thickness and gestational age and routinely used fetal growth parameters in the second and third trimesters. Additionally, we aimed to see if the placental thickness was lower in small for gestational fetuses.Methods This study was performed at a tertiary care center and was a prospective observational study. We recruited consecutive 200 pregnant women fulfilling inclusion and exclusion criteria. Using routine antenatal ultrasonography, we obtained several measurements of placental thickness, BPD, HC, FL, and AC. The placental thickness was measured at the level of umbilical cord insertion. The gestational age was calculated using last menstrual period.Results There was a strong correlation between placental thickness and gestational age (p < 0.001), BPD (p < 0. 001), HC (p < 0. 001), FL (p < 0. 001), and AC (p < 0.001) in both trimesters combined. In the second trimester, there was a strong correlation between placental thickness and gestational age (p < 0.001), BPD (p < 0.01), HC (p < 0.001), and AC (p < 0.001). In the third trimester, there was a strong correlation between placental thickness and gestational age (p < 0.001), BPD (p < 0.001), HC (p < 0.001), FL (p < 0.001) and AC (p < 0. 001). Patients delivering Small for gestational age (SGA) babies had significantly thinner placentas as compared to those with normal-weight babies (p < 0.001).Conclusions Placental thickness has a strong correlation with gestation age as well as BPD, HC, and AC in the second and third trimesters. Placental thickness is significantly lower in small for gestational age babies. Routine measurement of antenatal placental thickness using ultrasound can help predict gestational age and detect small for gestational age babies.