Assessment of gestational age using cerebellar measurements at cranial ultrasound: what is the best approach?

BACKGROUND AND AIMS

Clinical assessment of gestational age (GA) in preterm infants can be challenging. Several ultrasound approaches for estimating GA using cerebellar measurements are reported, claiming to be simpler and more accurate than clinical assessment, but they are not widely used. We aimed to compare the accuracy of four previously described measurements and compare their use in preterm infants.

METHODS

We studied infants <32weeks of GA defined by in-vitro fertilization date or early fetal ultrasound, excluding infants with neurological problems. Vermis anterior-posterior diameter (VAPD), vermis height (VH), and transverse cerebellar diameter via anterior (TCDa) and mastoid fontanelles (TCDm) were measured.Estimated PMA was calculated using published equations, and compared to known PMA using intraclass correlation coefficient (ICC). Intra and inter-observer reliability were determined.

RESULTS

We studied 80 infants (mean GA 28.5weeks [range 24-32], mean post-natal age 5.7days). ICC was 0.761 (VAPD), 0.632 (VH), 0.115 (TCDa) and 0.825 (TCDm). The TCDm equation gave the best estimate of GA (mean estimate -2days; 95% CI±13.8days). TCDa and TCDm absolute measurements were similar for each infant. Accuracy for estimating GA was similar for appropriately grown and small-for-gestation infants. Inter and intra-observer reliability was very good for all measurements.

CONCLUSIONS

Three previously described equations for estimating GA from cerebellar measurements gave good estimates of GA in preterms. The equation described for TCDm gave the narrowest 95% CI. We recommend the TCDm equation for the estimation of GA in VLBW infants but the TCD measurement can be made via either the anterior or mastoid fontanelle.