Placenta thickness: A sonographic index for foetal gestational age estimation

Abstract

A healthy placenta is crucial for foetal well-being, growth and development and neonatal survival. Foetal sonographic biometric parameters are crucial in obstetric decision making. This study correlated placenta thickness with foetal biometry in the estimation of gestational age (EGA) and estimated foetal weight (EFW). This was a prospective cross-sectional study in which 400 healthy pregnant women at gestational ages of 13 to 37 weeks, who attended antenatal clinic at the Lagos State University Teaching Hospital, were consecutively recruited. Obstetric ultrasound (USS) was performed to assess placenta thickness (PT), USS EGA and EFW in each study participant. Correlation of these parameters was done using Pearson’s correlation. A regression equation used to assess the relationship between PT and EGA was determined using linear regression analysis at confidence interval of 95% and p-value<0.05. The mean age of the women studied was 30.8±4.8 years. The mean PT ranged from 14.50±0.71 mm at 14 weeks to 36.58±1.54 mm at 37 weeks (wks). There was strong positive correlation between PT and USS EGA (r=0.968, p=0.000). A significant positive correlation was also noted between PT and EFW (r=0.900, p=0.000). There was no correlation between PT and maternal characteristics such as parity(r=-0.015, p=0.772) or maternal age(r=0.018, p=0.720). Ultrasound determined placenta thickness correlated linearly and positively with estimated gestational age and foetal weight. A regression equation of estimated PT was derived as follows; PT(mm) = 1.011 EGA (wks) – 0.663. Ultrasound determined placenta thickness correlates linearly and positively with estimated gestational age and foetal weight.