[Early transvaginal sonographic measurement of cephalic index].

BACKGROUND

The aim of this study is to obtain normal values of cephalic index by transvaginal scan early in pregnancy.

METHODS

In this prospective cross-sectional study, transvaginal high-resolution sonography was performed between 57 and 112 days' gestation in 1087 euploid fetuses. Measurements of cephalic index with standard deviations, calculated as the ratio biparietal diameter/occipito-frontal diameter, were obtained in the single gestational periods considered.

RESULTS

Cephalic index was found to show fairly constant values throughout the period evaluated with smaller values of standard deviation. The best correlation with gestational age was described by a linear correlation.

CONCLUSIONS

The data obtained by transvaginal scan can be used as parameters of normal values in early pregnancy.