Fetal cardiothoracic (C/T) circumference ratio is a parameter that can be used in the assessment of fetal cardiac and thoracic/chest wall anomalies. It is the ratio of the cardiac circumference to the thoracic circumference and may be easily measured on fetal ultrasound/echocardiography.
Radiographic features
Ultrasound/echocardiography
Classically, the C/T circumference ratio should be always <0.5 throughout gestation. It slowly increases throughout gestation 1,2:
~11 weeks: 0.38
~17-20 weeks: 0.45
term: 0.5
Increased C/T circumference ratios can be observed with either cardiac or thoracic pathology:
cardiac: fetal cardiomegaly
thoracic: pulmonary hypoplasia
Studies, however, have suggested that larger C/T ratios at later gestational ages may still be considered normal 3,4. These studies suggest appropriate cutoff ratios for cardiomegaly of:
12-15 weeks: 0.50
18-20 weeks: 0.52
25-30 weeks: 0.59
Unable to process the form. Check for errors and try again.