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What is Which of the following is the most common tumor of the fetus and newborn – and explain in detail?
Sacrococcygeal Teratoma (SCT) is the most common neoplasm in the fetus and newborn.

Sacrococcygeal Teratoma (SCT) is the most common neoplasm in the fetus and newborn with an estimated prevalence of 1:30,000- 1:40,000 and with a 3:1 female preponderance. - Handbook of Fetal Medicine by Shailesh Kumar (Cambridge Univ Press) 2010/87

Most common tumor in fetus and neonate → sacrococcygeal teratoma
Most common tumor in infancy → neuroblastoma