EXAMINATION OF REFERENCE RANGES OF THE ORBITAL DISTANCES FOR MONGOLIAN FETUS USING ULTRASOUND / Шинэ санаа Шинэ нээлт

ABSTRACT

Anomalies of the fetal orbit are caused by chromosomal and non-chromosomal abnormalities. The World Health Organization (WHO) recommended that the evaluation of the fetal growth and development using ultrasound to use their own national standard dimensions for obstetric and neonatal use. Nowadays, most countries have been using the own reference ranges for the fetal orbital dimensions in prenatal diagnosis for their nationality and ethnic group. In Mongolia, the extension of the standard parameters of biophetometer has been used for the fetus with 15-40 weeks of gestation. However, there is no study about fetal orbital dimensions. The purpose of our study was to determine the reference range of fetal orbital distances that can be diagnosed by ultrasound and to evaluate the relationships between the fetal orbital distances and the gestational ages (weeks).The study group included in 781 normal and fertility ages, pregnant women, which are relatively healthy and without any medical complications of pregnancy by prenatal examination of the routine ultrasound and genetic disorder at 16-36 weeks of gestation on a voluntary basis. Statistical analysis, including the linear regression and correlation were performed based on the obtained data.Correlations were observed between fetal orbital distances and the gestational ages. Strong linear relationships were observed between the fetal orbital (OD) (r= 0.81, p< 0.0001), biorbital (BOD) (r= 0.83, p< 0.0001), and inter-orbital (IOD) (r= 0.77, p < 0.0001)distances and the gestational ages (weeks). The fetal orbital distance (OD) was positively correlated with biparietal diameter (BPR) (r=0.77, p<0.0001), and the head circumference (HC) (r=0.83, p<0.0001). Moreover, strong correlations were observed between the biorbital distance (BOD) and the biparietal diameter (BPR) (r=0.804, p<0.0001), and the head circumference (HC) (r=0.86, p<0.0001). In addition, the inter-orbital distance (IOD) was positively correlated with biparietal diameter (BPR) (r=0.74, p<0.0001), and the head circumference (HC) (r=0.79, p<0.0001).The normal size of the orbital distance was slightly higher in Mongolian fetus compared to other countries. However, the inter-orbital distance was similar to other countries; and the bi-orbital distance was smaller in Mongolian fetus. These data may be helpful in the detection of fetal hypotelorism or hypertelorism.