Cranial and orbital growth in Chinese fetuses.

We assess Chinese fetal orbital growth by biparietal diameter (BPD) in normal pregnancies. One hundred and ninety-six normal fetuses, whose gestational periods ranged from 14 weeks to term, were measured by prenatal ultrasonography. Orbital parameters measured included orbital diameter (OD), biorbital distance (BOD), and interorbital distance (IOD). At the same time, fetal BPD was measured. The results show that orbital growth correlates well with BPD; OD versus BPD (r = 0.94, p less than 0.001), BOD versus BPD (r = 0.96, p less than 0.001), and IOD versus BPD (r = 0.83, p less than 0.001). Polynomial regression analysis demonstrates that the best-fit model for orbital parameters versus BPD was the first-order linear regression. From the above analysis, the 5th, 50th and 95th confidence limits of OD, BOD, and IOD were computed for specific growth values of BPD, and these can serve as a reference for prenatal diagnosis of fetal orbital malformations when menstrual age is not defined.