Comparative Study of TCD/AC and HC/AC Ratios in Predicting Fetal Growth Restriction

Fetal growth restriction (FGR) occurs when a fetus is not able to reach its genetic growth potential. This study aimed to compare the effectiveness of the trans-cerebellar diameter to abdominal circumference (TCD/AC) ratio versus the head circumference to abdominal circumference (HC/AC) ratio in predicting FGR.

The research was conducted in 200 pregnant women from March 2018 to May 2019 and included 40 women in their third trimester suspected of having FGR and 160 with normal fetal growth. Ultrasound measurements were taken for various fetal parameters, and the two morphometric ratios (TCD/AC and HC/AC) were determined and compared between the study and control groups. FGR diagnosis was confirmed through postnatal assessments, with newborn weights evaluated against Fenton's growth charts.

The results showed:

• The majority of cases (46.5%) were from the 26-30 age group and 23.5% in the group 31-35 years, 23% <= 25 years and 7% of the cases were >35 years.
• The clinical examination showed a sensitivity of 89.74%, specificity of 96.9%, positive predictive value of 87.5% and negative predictive value of 97.5%.
• The TCD/AC ratio demonstrated higher sensitivity (94.87%), specificity (99.37%), positive predictive value (97.36%) and negative predictive value (98.76%) compared to HC/AC.

In conclusion, although both TCD/AC and HC/AC ratios are effective, gestational age-independent parameters for detecting intrauterine growth restriction (IUGR), TCD/AC provides a superior diagnostic validity and accuracy for identifying asymmetric FGR.

Source:  Premarajan A, Narayanan S, Nair L, Shenoy H T, Transcerebellar diameter / abdominal circumference (TCD/AC) versus (HC/AC) head circumference / abdominal circumference --- USG prediction of fetal growth restriction? What do we observe in north Kerala, India. Indian J Obstet Gynecol Res 2024;11(4):563-570.