Reference Centile Charts for Ratio of Fetal Transverse Cerebellar Diameter to Abdominal Circumference in a Thai Population
Nitsana Singhakom MD*, Saifon Chawanpaiboon MD*, Vitaya Titapant MD*
Affiliation : *Department of Obstetrics and Gynecology, Faculty of Medicine Siriraj Hospital, Mahidol University
Objective : To establish the centile chart for the ratio of transverse cerebeller diameter to abdominal
circumference throughout pregnancy from 13-40 weeks
Design : Cross-sectional study.
Setting : Department of Maternal - Fetal Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University.
Subjects : The participants are women with gestational age between 13 and 40 weeks who attend Antenatal
Clinic, Siriraj Hospital.
Materials and Methods : A total of 643 pregnant women were recruited in this study. The exclusion criteria
were uncertained date of last menstrual period, multiple pregnancies, fetal abnormalities and maternal
conditions which could affect fetal growth. Transverse cerebellar diameter and abdominal circumference of
all the subjects were measured out by gestational age. The approximately equal numbers of fetuses were
measured at each week of gestation. The mean and standard deviation of TCD/AC ratio is estimated at each
week of gestation. In addition the 5th, 10th, 50th, 90th and 95th percentiles were calculated at each week of
gestation.
Results : Of 643 pregnant women, 149 (23.1%) were scanned before 20 weeks of gestation and 286 (44.5%)
were scanned between 20 and 30 weeks of gestation. The last group was intervened after 30 weeks of
gestation. TCD/AC ratio slowly declined from early pregnancy until about 20 weeks then remained stable.
After 30 weeks of gestation it started to decline again.
Conclusion : The normal reference value of TCD/AC ratio in Thai fetus were shown in this study. This ratio
can be used to calculate gestational age in intrauterine growth restriction fetus.
Keywords : TCD/AC ratio, Reference centile chart , Thai fetus
