Reliability of trans-cerebellar diameter for gestational age in comparison to crown rump length

Abstract

Background and objective: accurate estimation of gestational age is important for perfect antenatal care, as many pregnant women may don’t know their last menstrual period & not have a first-trimester ultrasound that is accurate in estimating the gestational age, and the routine fetal biometry in the second & third trimesters may be unreliable for some reason. Therefore, it’s necessary to develop an ultrasonographic parameter capable of reliably estimating gestational age at any point during pregnancy. This study aims to compare the accuracy of trans-cerebellar diameter (TCD) in n 2nd and 3rd trimesters for the calculation of estimated gestational age with the first-trimester crown rump length (CRL) which is the most accurate measurement for the estimation of gestational age. Methods: This is a prospective study conducted in Erbil from the 1st of January 2021 to the 10thof August 2022. A total sample of 258 antenatal women was included. The ultrasound examination was performed by a GE Voluson ultrasound system (GE health care 2015) machine using a 3.5 MHZ curved transducer. The CRL was taken between 6-13 weeks of gestational age, and TCD between 15-38 weeks. TCD is measured by keeping the calibers on the outer margin of the cerebellar hemisphere. Data were analyzed using the statistical package for social science SPSS V. 26. Results: The mean transcerebral diameter during different gestational ages was 16.35 (±0.76) less than 18 weeks gestation, 21.48 (±1.7) between 18-25 weeks gestation, 28.03 (±1.79) between 25-32 weeks gestation, 35.52 (± 1.84) above 32 weeks gestation respectively. There is a statistically significant linear correlation between TCD and ECRL with (rho=0.992) (P <0.001) Conclusion: The accuracy of the TCD in the second & third trimester of pregnancy is comparable with the estimated CRL in the first trimester, so this will help us in the estimation of the gestational age for pregnant women with unknown LMP and unavailable first-trimester dating scan.

Keywords

• crown-rump length
• trans-cerebellar diameter
• estimated gestational age
• 1st trimester
• 3rd trimester