• Faiza Naseem, Naheed Fatima, Shakeela Yasmeen, and Saima Saleem.
• Department of Obstetrics and Gynaecology, Bahawal Victoria Hospital, Bahawalpur. adilgemini@gmail.com
• J Coll Physicians Surg Pak. 2013 May 1; 23 (5): 322-5.

ObjectiveTo determine the frequency of correct assessment by transcerebeller diameter (TCD) versus biparietal diameter (BPD) for gestational age measurement at 36 weeks of pregnancy using first day of last menstrual period (LMP) for actual period of gestation.Study DesignQuasi experimental.Place And Duration Of StudyDepartment of Obstetrics and Gynaecology, Bahawal Victoria Hospital, Bahawalpur from May to November 2010.MethodologyThis study was performed on 228 patients at 36 weeks of pregnancy fulfilling the inclusion criteria. Ultrasound measurements of TCD and BPD was made and compared with LMP. Collected data was analyzed by SPSS version 10. Proportoin of correct diagnosis by each measurement was determined and compared using chi-square test with significance at p < 0.05.ResultsOut of 228 patients, TCD was found to give correct assessment in 209 patients (91.7%; p = 0.001) corresponding to the gestational age by LMP i.e 36 weeks. BPD was found to give correct assessment corresponding to the gestational age by LMP in 176 patients (77.2%).ConclusionAlthough both BPD and TCD are accurate biometric parameters at 36 weeks of gestation, transcerebellar diameter is more reliable method of gestational age determination in third trimester of pregnancy than biparietal diameter. TCD can be used as a tool to assist in the assessment of gestational age in third trimester.

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