# Gestational age determination in neonates - transcerebellar ultrasound measurements help: a retrospective study of 671 neonates

## TL;DR

This study shows that measuring a baby's cerebellar width after birth can reliably estimate gestational age, similar to prenatal methods.

## Contribution

The study demonstrates that neonatal transcerebellar diameter measurements can reliably estimate gestational age using fetal charts as a reference.

## Key findings

- Neonatal transcerebellar diameter measurements matched fetal chart estimates of gestational age.
- There was no significant difference in GA estimation between neonates up to 10 or 21 days old.
- The method could improve GA estimation for neonates with unknown maternal last menstrual period.

## Abstract

Many children are born without prenatal determination of gestational age (GA). Postnatal determinations are limited. Fetal GA determination using transcerebellar diameter measurements is reliable for fetuses. We wanted to see if transcerebellar diameters obtained on neonatal head ultrasound exams could help GA determination in newborns and whether such measurements conformed to similar GA determinations in fetuses.

Our goal was to determine if neonatal GA can be estimated by measuring transcerebellar diameter via a transmastoid approach using fetal charts as the gold standard. If true, one could develop a neonatal chart for GA determination by transcerebellar diameter.

Transmastoid views are a routine part of our neonatal intensive care unit neurosonograms. A retrospective analysis of transcerebellar diameters of neonates (1 day to 21 days old) born between 22 weeks and 40 weeks corrected GA was performed. Cases with congenital anomalies, intraventricular hemorrhage, or other neurosonographic abnormalities were excluded. Neonatal GA was determined by early antenatal crown rump lengths. We calculated transcerebellar mean and standard deviation for each prenatally determined GA week. GA was determined from fetal charts, both for subsets of neonates evaluated at less than or equal to (≤) 10 days of life and for those examined at ≤21 days of life. Statistical analysis using linear regression demonstrated no differences in GA determined by neonatal transcerebellar diameter compared to fetal charts (our gold standard).

We evaluated 1,260 neurosonograms. Of these, 589 cases were excluded. A total of 671 exams were of neonates ≤21 days old; 530 of those were examined at ≤10 days of life. There were no significant differences between GA determined by fetal charts and our neonatal transcerebellar diameters, whether from the ≤21-day (P=0.15) or the younger ≤10-day group (P=0.87).

Neonatal GA estimation by transmastoid fontanelle measurements of cerebellar width appears as reliable as the accepted antenatal transcerebellar measurements of fetuses. Our proposed neonatal chart will hopefully aid reliable estimation of GA in neonates, improving patient care among neonates with unknown maternal last menstrual period.