Fetal transverse cerebellar diameter/abdominal circumference ratio in assessing fetal size.

OBJECTIVE

To test the usefulness of the fetal transverse cerebellar diameter/abdominal circumference (TCD/AC) ratio in predicting known small-for-gestational-age (SGA) infants.

METHOD

The relationship between fetal TCD and AC throughout the second half of pregnancy was investigated in 635 well-dated, normal pregnancies and examined with regard to gestational age and infant birth weight percentiles.

RESULTS

One hundred eighteen (19%) fetuses were excluded due to inadequate visualization of the fetal cerebellum. A strong correlation was noted between gestational age determined by the last menstrual period and both fetal TCD (r2 = 0.91338) and AC (r2 = 0.89361) in fetuses with birth weights between the 10th and 90th percentiles (n = 407; mean 14.4, S.D. 1.2). Although the TCD/AC ratio showed a poor correlation with gestational age (r2 = 0.15788), a slight increase was noted during gestation. A TCD/AC ratio greater than 15.5 was present in 80% of SGA infants when measurements were performed within 1 week of delivery.

CONCLUSION

Fetal TCD/AC ratio as a gestational age-independent method could improve diagnostic sensitivity and specificity in the early detection of fetal growth abnormalities.