Objectives: Our study sought to determine the effect of age, parity, body mass index (BMI), and previous oral contraceptive use on gallbladder volume and ejection fraction in pregnancy to enable obstetricians to identify patients at risk of gallbladder disease in pregnancy. Methods: We conducted a prospective cross-sectional study involving 190 pregnant women who were evaluated within 32 and 40 weeks gestation at the Fetal Assessment Unit of the Department of Radiology, University of Ilorin Teaching Hospital, Nigeria. Patients were scanned with a commercially available Siemens Ultrasound scanner using a curvilinear probe and a transducer frequency of 3.5 MHz. The fasting gallbladder volume (FGBV) and 30 minutes postprandial gallbladder volume (PGBV) were calculated using the prolate ellipsoid method. Gallbladder ejection fraction was determined using FGBV and PGBV. Each patient's biodata, medical history, and somatometric parameters were documented. Results: A total of 190 volunteers were included in the study. BMI showed statistically significant positive, though weak correlations with FGBV (r = 0.179, p = 0.015) and PGBV (r = 0.216, p = 0.003). Maternal age, parity, and previous oral contraceptive use did not show any statistically significant correlation with gallbladder parameters. Conclusions: BMI showed a statistically significant but weakly positive correlation with FGBV and PGBV in pregnancy. Our study demonstrated that gallbladder volume in pregnancy might be dependent on BMI. Thus, high BMI may predispose to large gallbladder volume, increasing the risk of biliary stasis and gallstone formation in pregnancy. This is relevant for early detection and prevention of gallbladder disease and follow-up, including expectant management of subjects that may develop gallbladder disease in pregnancy.