Placental thickness in 2D prenatal ultrasonographic examination

The placental thickness (PTh) is an ultrasonographic measurement commonly used to assess the placenta. The study aimed to determine selected factors influencing PTh in 2D prenatal ultrasonographic examination. It might have a special value in difficult cases for interpretation when PTh is above or below the reference values.

In this retrospective study, we analysed the results of foetal ECHO examination of 2833 foetuses performed between June 2016 and December 2019 in our single unit. 596 healthy foetuses older than 12 weeks of gestation from singleton pregnancies were enrolled in the study. The following parameters were used in the further analysis: placental implantation site, gestational age according to the last menstrual period (LMP) and foetal biometry (FB); maternal weight, height, and body mass index (BMI) at the time of examination; and PTh.

PTh was affected by its location: posterior 33 mm vs. anterior 30 mm (p < 0.001). Moreover, its thickness significantly correlated with gestational age according to FB (r = 0.386, p < 0.001), LMP (r = 0.369, p < 0.001), maternal weight (r = 0.192, p < 0.001), height (r = 0.125, p = 0.002), and BMI (r = 0.147, p < 0.001), but not with maternal age (r = 0.050, p = 0.219). A linear regression model based on these data explained the 16.38% variability of the tested subjects (p < 0.001).

Our observations suggest that maternal weight correlated more strongly with PTh than maternal BMI. For PTh evaluation, it is important to pay attention to the placental implantation site - the posterior placenta was thicker than the anterior placenta. Moreover, PTh variability remains largely unknown; therefore, further research in this field is needed.