Journal of Institute of Medicine, April, 2010; 32:1
Fetal transcerebellar diameter nomogram in Nepalese
B. R. Joshi
Department of Radiology and Imaging, Tribhuvan University Teaching Hospital, Kathmandu, Nepal.
Correspondance to : B. R. Joshi, Department of Radiology and Imaging, Tribhuvan University Teaching Hospital,
Introduction: Sonographic determination of gestational age (GA) is becoming increasingly important.
Many parameters can be used for establishing GA. The transverse cerebellar diameter (TCD) is a
reliable parameter for estimating it. Fetal cerebellum grows progressively along with GA and can
predict GA at any trimester. This study was undertaken to construct an institution specific
Transcerebellar diameter (TCD) nomogram and to compare its ability to predict gestational age with
previously published nomograms.
Methods: A cross-sectional nomogram was constructed using TCD measurements of 594 singleton
fetuses in Nepalese population by using linear regression model. Measurements were obtained by
placing the calipers of the ultrasound machine at the outer – to- outer margins of the cerebellum. The
suitability of previously established TCD nomograms for predicting gestational age was assessed in
Nepalese population to determine comparability between nomograms.
Results: Gestational age and TCD 50th percentile in mm coincided well till 20th week of gestation.
Between 21st to 28th weeks of gestation, there were no clinically important differences between our
nomogram and previously published in terms of the predicted gestational age. However, predicted
gestational age in third trimester was considerably different by using our nomogram by 1-2 weeks
from 29-32 weeks and by 3-6 weeks after 33 weeks. There were differences of 4-6 mm between 29-32
weeks and of 7-11 mm after 33 weeks.
Conclusions: TCD measurements had a similar relationship with gestational age across previously
published nomograms before 28 weeks. Significant differences occurred in predicting gestational
age after 33 weeks.
Keywords: Gestational age, nomogram, transcerebellar diameter, ultrasound
Estimation of length of gestation is of critical importance in
clinical practice to ensure appropriate management of
newborns and to distinguish pre-term from term infants.
Low birth weight, a common problem in developing
countries, is due to either short gestation or to being small
or light-for-date. Clinical problems encountered with short
gestation (pre-term) whose birth weights match their GA
are hyaline membrane disease and infection. Small for dates,
whether pre-term or term, are liable to suffer from asphyxia
and hypoglycemia during the course of labor and
immediately post-delivery. In addition, post-maturity
problems may arise when mothers are not aware of last
menstrual period (LMP) and appropriate care is not provided
to reduce complications such as asphyxia or hypoglycemia.1
Despite recognition that estimation of GA based on maternal
recollection of the LMP is fraught with error, it is not
generally appreciated that the magnitude and direction of