Tumor volume to fetal weight ratio as an early prognostic classification for fetal sacrococcygeal teratoma

Purpose This study was designed to develop a prognostic factor for fetuses with sacrococcygeal teratoma (SCT) that may be useful to predict outcome and guide counseling early in pregnancy. We hypothesize that, in fetuses with SCT, the ratio of tumor size to estimated fetal weight in the second trimester predicts outcome. Methods We retrospectively reviewed charts of all patients evaluated at our Fetal Center for SCT between 2004 and 2009. Estimated fetal weight and tumor volume were calculated based on prenatal ultrasound or fetal magnetic resonance imaging. Patients were stratified based on tumor volume to fetal weight ratio (TFR), and their outcomes were analyzed by Fisher's Exact test. Results Tumor volume to fetal weight ratio before 24 weeks' gestation was predictive of outcome. Those with a TFR less than or equal to 0.12 (n = 5) had a significantly better outcome than patients with a TFR greater than 0.12 (n = 5, P < .05). All patients with poor outcomes had a TFR greater than 0.12 by 24 weeks' gestation. A TFR greater than 0.12 predicted poor outcome with 100% sensitivity and 83% specificity. All 4 patients who developed hydrops had a TFR greater than 0.12. Conclusion In our series of fetuses with SCT, TFR before 24 weeks' gestation correlates with outcome. This novel, prenatal diagnostic tool may be useful in prenatal counseling and for early identification of high-risk fetuses.