Backgroung: Estimating fetal weigh essential in our daily obstetric practice, especially at third trimester. It guides obstetricians to make up their decisions regarding time and mode of delivery.One of the most important factors affecting birth weight can be attributed to placental adequacy and uterine environment. The placental thickness is one of the characteristics of the placenta therefore, we decided to study the correlation between the placental thickness and the fetal birth weight. Methods: this is a cross sectional prospective observational study that was conducted on 200 uncomplicated pregnant women in their third trimester.  Ultrasound was done for measuring the placental thickness (PT), bi-partial diameter (BPD), head circumference (HC), femur length (FL), abdominal circumference (AC) and estimated fetal weight. After delivery the birth weight was measured. Apgar score, NICU admission and Neonatal morbidity and mortality were observed.  Results: The study found that there were positive significant correlations between placental thickness and estimated fetal birth weight r=0.899 and between placental thickness and actual birth weight r=0.933 both with p value <0.001.Conclusion: Placental thickness can be used as a promising parameter in predicting expected fetal birth weight (EFBW) with other fetal parameters during antenatal follow up by ultrasound.