The cardiofemoral index (CFI) can be used as a noninvasive marker for fetal anemia in pregnancies with isoimmunization.



(1) biventricular outer dimension (BVOD) in cm

(2) femur length in cm


The BVOD is taken by:

(1) M-mode ultrasound cursor is set perpendicular to the interventricular septum at the atrioventricular valves.

(2) The image is frozen in diastole.

(3) The distance beween the right and left epicardia is measured.


cardiofemoral index =

= (biventricular outer dimension in cm) / (femur length in cm)


Interpretation based on the study of Cabral et al:

• The CFI is 0.57 +/- 0.1 (0.47 to 0.67) if no anemia is present.

• The CFI is 0.64 +/- 0.16 (0.48 to 0.80) with mild anemia.

• The CFI is 0.72 +/- 0.13 (0.59 to 0.85) with severe anemia.

• A CFI > 0.59 can help to identify a high-risk fetus who may benefit from an intrauterine transfusion.


Performance (in the study of Cabral et al):

• The sensitivity for severe anemia was 94%.

• The false positive rate was 44%.

• A higher cutoff would be less sensitive but more specific.

• The AUC for the selected cutoff was 0.75.


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