Background: Good Antenatal Care requires monitoring of pregnancy through meticulous history, examination and investigation. Ultasound is a non-invasive, safe, economical and easlily accessible test, routinely used to monitor Maternal and Foetal well-being. Vigilant obstetric care depends on accurate dating of pregnancy and timely interventions which are gestational age dependent. Gestational age is calculated from first day of last menstrual period to the current date (Naegle’s formula). Early pregnancy ultrasound using Gestational Sac Diameter (GSD) and CRL is accurate in dating pregnancy where a pregnant woman is not sure of menstrual cycles or the cycles are irregular.1 Sonographic Monitoring utilizes foetal biometry to study fetal anatomy through different parameters like Crownrump length (CRL), fetal bi-parietal diameters (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) to determine gestational age (GA), fetal weight, and growth in different trimesters of pregnancy and to rule out the presence of congenital anomalies.2,3

There have been studies on BPD and assessment of gestational age, that have shown anthropological variations. Socioeconomic, demographic and environmental factors also play an important role in taking timely decisions which are dependent on correct gestational age

Aims and Objectives: This study aimed to ascertain correlation between BPD and gestational age in pregnant females visiting ANC OPD of Rural Health and Training Centre at Jawan, Aligarh.

Methodology: The study enrolled 100 consecuetive pregnant females attending ANC OPD of RHTC, Jawan, Aligarh. They had their routine antenatal ultrasound, which were assessed for the BPD data.

Inclusion Criteria: Study included pregnant females without any medical conditions that can complicate the pregnancy.

Exclusion Criteria: Refusal of consent, twins, medical disorders of pregnancy, congenital anomalies

Conclusion: This study was done in North India rural population with the mean age of pregnant females of 26 years. It showed a linear correlation between BPD and gestational age. BPD was found to have a positive correlation with gestational age especially in second trimester. The accuracy in predicting gestational age declines with the advancing gestation. Thus, ultrasonographic measurement of biparietal diameter can be used to used to predict gestational age in Indian foetuses.