Abstract Objective: Presently, the usual upper limit of lateral cerebral ventricular atrium is 10 mm. and if it is more than 10mm, so it necessitate more radiological appraisal to rule out ventriculomegaly. The aim in this study is measure the mean diameter of the fetal lateral cerebral ventricular atrium during the last two trimesters through utilization of transabdomenal ultrasonography in Babylon province. Method: In this perspective cross sectional study 151 fetus in their 2nd and 3rdintrautrin live were included and trans-abdominal ultrasonagraphy was performed for all those fetuses to measure their cerebral lateral ventrical size. Results: The mean age of all participant women was 25.2 ± 5.8 years, primigravida constitute 25% of the participants women (N=37) while the multigravida pregnant ladies constitute 75% (N=114). The mean of the lateral ventricular diameter of the whole study (male and female) and in both 2nd and 3rd trimester was 7.15 ± 1.32mm, there was significant correlation between the LV diameter and the head circumference (r, p=0.088, 0.04). Conclusion: Left ventricular diameter of 10mm is considered as upper limit for its normal size, any measurement more than 10 mm should be considered as alarming sign and may nesses ate further investigations.