Acardiac twin pregnancies part II: Fetal risk of chorangioma and sacrococcygeal teratoma predicted by pump/acardiac umbilical vein diameters

Background: We recently published pump/acardiac umbilical venous diameter (UVD) ratios, representing the pump twin's excess cardiac output fraction, of 27 acardiac twin pregnancies. There was a clear separation between the 17 pump twins that had life-threatening complications and the 10 that did not. The hypothesis of this study is that placental chorangioma and sacrococcygeal teratoma (SCT), tumors whose perfusion also causes high-output complications, have the same fetal outcome as pump twins when perfusion of the tumor requires the same excess cardiac output fraction. Methods: We compared the three fetoplacental circulations. Fetuses with a placental chorangioma and acardiac twin pregnancies both have their feeding artery and draining vein located at the placental cord insertion. In contrast, SCT lacks a prescribed feeding artery and draining vein. We, therefore, had to modify our model to assume that the diameter of the hypothetical draining vein is related to the flow difference between inferior vena cava and superior vena cava. The latter flow has been estimated sonographically and is the same as the inferior vena cava flow in the absence of an SCT. Furthermore, a simple modification accounts for the different location of the tumor with respect to the placental cord insertion. Results: We propose to apply the clinical pump/acardiac UVD ratios to pregnancies complicated by placental chorangiomas and the modified pump/acardiac UVD ratios for SCT. Conclusion: Risk prediction of these rare fetal tumors may be possible based on application of data on excess cardiac output fractions from pump/acardiac UVD ratios and will require future clinical validation.