Assessment of placental thickness as a predictor of gestational age and fetal weight in second and third trimester of pregnancy

Background: Estimation of precise gestational age as well as fetal weight is important and is usually done by ultrasound assessment of fetal biometry. Recently estimation of placental thickness as a marker of fetal maturity as well as fetal weight has become a topic interest amongst obstetricians because of the accuracy with which placental thickness can be used for estimation of gestational age. We undertook this observational study to find out whether placental thickness can be used for estimation of gestational age and fetal weight in healthy singleton pregnancies. Methods: This was a prospective observational study in which 210 patients in second and third trimester of pregnancy who has undergone antenatal ultrasound examination were included on the basis of a predefined inclusion and exclusion criteria. First gestational age estimation was done using fetal biometry (head circumference, biparietal diameter, abdominal circumference and femur length). Placental thickness was measured at the level of cord insertion. Correlation between placental thickness and gestational age as well as fetal weight as determined by biometry was analyzed by pearsons coefficient. P value less than 0.05 was taken as statistically significant. Results: Mean age of studied cases found to be 24.62±4.12 years. Mean gestational age of the studied cases was found to be 28.19±6.90 weeks. The most common location of placenta was anterior which was seen in 99 (47.14%) patients followed by posterior (32.38%) and fundal (10.95%). Analysis of mean placental thickness in studied cases showed that at 12 weeks of gestation the mean placental thickness was 12.96 mm. Mean placental thickness at 37 weeks found to be 36.82 mm and this value was determined to be cut-off value for differentiating between full term and preterm gestation. There was strong positive correlation between placental thickness and gestational age between 12-38 weeks. Similarly positive correlation also existed between placental thickness and gestational age between 14-37 weeks. Conclusions: Placental thickness can be used for estimation of gestational age as well as fetal weight in cases where fetal biometry can not be entirely relied upon.