title: Normal ranges of biorbital and interorbital distances in healthy Turkish pregnancies at 19-23 weeks of gestation and correlation with craniofacial structures.
abstract: 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.
  
  
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Obstetrics and Gynecology, Division of Perinatology, Celal Bayar University Faculty of Medicine, Manisa, Turkey.
authors.forename: Halil Gürsoy
authors.initials: HG
authors.lastname: Pala
authors.affiliation: Department of Obstetrics and Gynecology, Division of Perinatology, Celal Bayar University Faculty of Medicine, Manisa, Turkey.
authors.forename: Burcu
authors.initials: B
authors.lastname: Artunç-Ülkümen
authors.affiliation: Department of Obstetrics and Gynecology, Division of Perinatology, Celal Bayar University Faculty of Medicine, Manisa, Turkey.
authors.forename: Faik Mümtaz
authors.initials: FM
authors.lastname: Koyuncu
authors.affiliation: Department of Obstetrics and Gynecology, Division of Perinatology, Celal Bayar University Faculty of Medicine, Manisa, Turkey.
authors.forename: Yıldız
authors.initials: Y
authors.lastname: Uyar
authors.affiliation: Department of Obstetrics and Gynecology, Division of Perinatology, Celal Bayar University Faculty of Medicine, Manisa, Turkey.
authors.forename: Yeşim
authors.initials: Y
authors.lastname: Bülbül-Baytur
keywords: Biorbital distance; Turkish population; interorbital distance; mid-trimester scan