Placental Thickness: Its Correlation with Ultrasonographic Gestational Age in Normal and Intrauterine Growth-Retarded Pregnancies in the Late Second and Third Trimester

Objective

The aim was to study the correlation of placental thickness, measured at the level of the umbilical cord insertion, with the ultrasonographic gestational age in normal and IUGR pregnancies in the late second and third trimester.

Materials and Methods

A total of 498 patients were observed for correlation of the placental thickness with ultrasonographic gestational age and their outcomes by dividing them into Group A (outcome fetal weight < 2,500 g, n = 122) and Group B (fetal weight > 2,500 g, n = 376). The mean placental thickness was calculated at the umbilical cord insertion in both groups along with ultrasonographic fetal age and estimated fetal weight. The mean values of placental thickness along with respective standard deviation were calculated from the 24th to 39th week of gestational age.

Results

A positive correlation was observed between placental thickness and ultrasonographic gestational age in both groups (p value of 0.01), with Pearson’s correlation coefficient (“r”) values of 0.325 in Group A and 0.135 in Group B. Regression analysis yielded linear equations of relationship with placental thickness and gestational age in both groups. The placental thickness was also found to be lower in Group A between 26 and 27 weeks and 30 and 31 weeks, having mean values of 2.48 ± 0.063 cm (p value of 0.042) and 2.76 ± 0.552 (p value of 0.05) in Group A as compared to 3.04 ± 0.25 and 3.13 ± 0.183 cm in Group B.

Conclusions

Placental thickness measured at the level of umbilical cord insertion can be used as an accurate sonographic indicator in assessment of gestational age in singleton pregnancies because of its linear correlation.