Introduction: To choose whether to end the pregnancy and how to deliver the baby, obstetricians require a precise estimation of gestational age. Other criteria can be useful when inaccurate menstrual history cannot be utilized to estimate gestational age. One such element is the fetal sacral length, which may be measured using ultrasound. Numerous criteria have been utilized in conjunction with ultrasonography to estimate gestational age. However, only the first and second trimesters of pregnancy are when all of these metrics are trustworthy. They become less accurate as the pregnancy goes on for a number of reasons, with the third trimester having the most fluctuation at around 3 to 3.5 weeks. Methods: A total of 200 pregnant women participated in this prospective observational study at the Department of Radiology and Imaging, Bangladesh Institute of Research and Rehabilitation in Diabetes, Endocrine and Metabolic Disorders. The research was carried out between January 2001 and December 2002. Result: The participants' average age was 24.54 years. Only 3% of the participants were in the oldest age range of 36-40 years, with 38 percent of the participants being between the ages of 21 and 25. The average height of the participants was 150-154 cm in 52 percent of the cases. The mean SD height and weight were 152.40±3.44 cm and 54.80±4.45 kg, respectively. There is a strong positive relationship between fetal sacral length and gestational age, according to BPD and FL. The relationship between gestational age and fetal sacral length was demonstrated to be statistically significant. There was no statistically significant relationship between fetal sacral length and maternal height. Conclusion: Fetal sacral length and gestational age are closely connected. Sacral length can be used consistently as an extra metric during pregnancy in conjunction with other established parameters if it is assessed precisely with a high-resolution ultrasound scanner.