Background: Accurate estimation of gestational age is essential for proper antenatal care and fetal growth assessment. While conventional biometric parameters such as biparietal diameter and femur length are widely used, fetal orbital biometry has emerged as an additional reliable tool. This study aimed to evaluate the correlation between fetal orbital parameters—binocular distance (BOD), inter-ocular distance (IOD), and orbital diameter (OD)—and gestational age during the second and third trimesters.

Objective

Primary objectives

1.       To measure fetal orbital parameters binocular distance (BOD), orbital diameter (OD) and inter-ocular distance (IOD).

2.       To derive statistical correlation between fetal orbital parameters and Gestational age by USG.

Secondary objective

1.       To determine Gestational age by LMP (Last menstrual period) and other biometric parameters calculated from ultrasonography

Methods: A cross-sectional study was conducted in the Department of Radio-diagnosis, KVG Medical College and Hospital, Sullia, over 18 months from March 2024 to August 2025. A total of 120 healthy pregnant women with singleton pregnancies between 13 and 38 weeks of gestation were included. Fetal orbital parameters were measured using ultrasonography on GE Voluson S8 Pro and Philips Affinity 70G machines. Gestational age was calculated by both last menstrual period (LMP) and ultrasonography. Statistical analysis was performed using SPSS version 23.0.

Results: The mean gestational age by LMP was 22.11 ± 5.75 weeks and by USG was 22.16 ± 5.76 weeks, with no significant difference (p = 0.9464). The mean BOD, IOD, and OD were 35.62 ± 9.74 mm, 11.10 ± 3.02 mm, and 12.21 ± 3.33 mm, respectively. All parameters showed a linear increase with advancing gestation and a strong positive correlation with gestational age, most significantly for BOD (r = 0.9938, p < 0.0001).