Normal ranges of biorbital and interorbital distances in healthy Turkish pregnancies at 19-23 weeks of gestation and correlation with craniofacial structures

Objective: We aimed to determine the normal ranges for biorbital (BOD) and interorbital distances (IOD) during the second trimester in Turkish women with normal pregnancies and to assess the correlation between BOD, IOD, and other fetal craniofacial structures and biometric parameters.

Material and methods: Our retrospective study comprised 1328 women with singleton normal pregnancies who had undergone ultrasonography (USG) examinations at 19-23 weeks of gestation in the second trimester screening. The measurements of BOD and IOD were obtained with the coronal section of the fetal face at the plane of orbits.

Results: Mean BOD was 3.4±0.33 cm, whereas mean IOD was 1.28±0.24 cm. Correlation analysis revealed that BOD was significantly correlated with IOD, transcerebellar diameter (TCD), cisterna manga (CM), nuchal fold (NF), nasal bone (NB), biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), and gestational week. There was a significant relation between IOD and the lateral ventricle posterior horn, TCD, CM, NF, NB, BPD, HC, AC, and FL.

Conclusion: The reference ranges obtained in our study enabled accurate evaluation of BOD and IOD in the second trimester of normal pregnancies. USG detection of fetal orbital biometric anomalies may alert the clinician for different anomalies associated with abnormal development of eye.