The accuracy of placental thickness in estimation of gestational age during late third trimester - A single centre...

To determine the validity of the placental thickness for calculating the gestational age during the third trimester.

A cross-section prospective study was carried out from March 2019 to January 2020 at the Obstetrics and Gynaecology Department in Al Yarmouk Teaching Hospital, Baghdad, Iraq on 90 women with low risk pregnancy and gestational age between 34 to 37 completed weeks, recruited from the antenatal clinic. The foetal gestational age was estimated by the accurate date of the last menstrual period and early ultrasound at 11-14 weeks of gestation. Placental thickness was determined at the umbilical cord implantion site. The association between placental thickness and gestational age was established.

There was no meaningful association amongst placental thickness and age, gravida, para, and placental location. The mean placental thickness in this analysis was 34.17mm at 34th week of gestation to 34+6 days, and its steadily (and significantly) increased through 35th to 35+6 days, and from 36week to 36+6days ,and 37th weeks of gestation, (35.06, 36.11, and 36.81 millimeters; respectively).Placental thickness in millimeters had a linear relationship and a statistically significant positive correlation with gestational age (in weeks) in the third trimester. A cut off placental thickness more than 36.3 mm can be used to differentiate between term and preterm pregnancy.

Mean placental thickness was steadily and significantly increased through third trimester of pregnancy, and can be used as a parameter for accurate estimation of gestational age during third trimester of pregnancy. A more than 36.3 mm placental thickness can be used as cut off point between term and preterm pregnancy.