The CVR increases with gestational age because it results from the division of two parameters of different dimensions, with a resulting quadratic equation. Thus, the size of the CPAM necessary to produce a CVR greater than 1.6 cm2 decreases with gestational age. Therefore, the use of a fixed value of the CVR, e.g. 1.6 cm2, to predict fetal hydrops or neonatal demise, is inappropriate. A different ultrasound index that is independent of gestational age should be used in the counseling of patients with CPAM.
Kontopoulos et al. (Mon,) studied this question.