Comparing the Reliability of Trans-Cerebellar Diameter with Other Fetal Biometrics for Gestational Age Estimation

Abstract

Comparing the Reliability of Trans-Cerebellar Diameter with Other Fetal Biometrics for Gestational Age Estimation

Shilee J. Goshit¹, Nyango D. Dalyop¹, Amaka N. Ocheke¹

Abstract

Background: Accurate estimation of gestational age is critical in obstetric care decision-making, especially when managing high-risk pregnancies. It is indispensable in developing countries where most antenatal care women book late.

Objectives: To determine the accuracy and reliability of trans-cerebellar diameter as a method of estimating gestational age in the second trimester of pregnancy.

Methods and Materials

This was a hospital-based cross-sectional study. The respondents were 384 ANC women carrying singleton and uncomplicated pregnancies in the second trimester who presented for booking at the JUTH between 1^st January 2020 and 31^st March 2020. The respondents were women between 15- 26 weeks of gestation and who were either sure of their last menstrual periods or had an early obstetrics ultrasound scan done on or before 20-22 weeks of gestation. They were recruited using convenience sampling method until the sample size was reached. Interviewer-administered semi-structured questionnaire was used to gather data on socio demographic characteristics, obstetric history, gestational age, LMP, previous history of contraceptive use, menstrual history, and co-morbidities and ultrasound scan results. The estimated gestational age was calculated using the Naegele’s rule and the fetal biometric parameters were measured using GE Voluson P8-BT19 ultrasound machine with a RAB6-RS 4-8.5 MHz Real Time 4D Convex Transducer. Fetal biometric parameters including, TCD, BPD, HC, AC and FL were measured in 2D mode. Data was subjected to descriptive and inferential statistical analysis using Statistical Package for Social Sciences (SPSS) version 23 (SPSS Inc, Chicago, IL).

Results

The mean GA was 21.1 +3.1 weeks, with a bimodal GA distribution of 20.1-21, and 25.1-26 weeks. Two hundred and thirty-nine respondents (62.2%) were sure of their last menstrual period and 145 (37.8%) had a first trimester ultrasound scan. The mean age of the participants was 29.1+5.7 years. There was significant correlation between TCD and menstrual GA (r = 0.963; p<0.05). The correlation between TCD and GA was better than the other four parameters at 95% confidence interval. This correlation was further corroborated by the student t-test. The composite ultrasound GA however had a better correlation than TCD alone-r = 0.969.

CONCLUSION

TCD is a reliable method of gestational age estimation. It is superior to BPD, HC, AC and FL in the second trimester of pregnancy, but less accurate than the composite GA.

Key Words: Trans-cerebellar diameter, Gestational age, Ultrasound, Second trimester, Nigeria