▁F etal ▁tum ors ▁present ▁during ▁pr en atal ▁ul tras ound ▁ex ams , ▁with ▁or ▁without ▁mat ernal ▁sympt oms . ▁ ▁S CT s ▁found ▁during ▁routine ▁ex ams ▁tend ▁to ▁be ▁small ▁and ▁partly ▁or ▁entirely ▁external . ▁ ▁The ▁internal ▁S CT s ▁are ▁not ▁easily ▁seen ▁via ▁ul tras ound , ▁unless ▁they ▁are ▁large ▁enough ▁to ▁reve al ▁their ▁presence ▁by ▁the ▁ab normal ▁position ▁of ▁the ▁f etal ▁ur inary ▁bl ad der ▁and ▁other ▁org ans , ▁but ▁large ▁f etal ▁S CT s ▁frequently ▁produce ▁mat ernal ▁comp lications ▁which ▁necess itate ▁non - rout ine , ▁investig ative ▁ul tras ounds . ▁ ▁Ne on atal ▁tum ors ▁present ▁at ▁birth ▁pro tr ud ing ▁from ▁the ▁sac ral ▁site ▁and ▁are ▁usually ▁m ature ▁or ▁imm ature ▁ter atom as . ▁Among ▁inf ants ▁and ▁young ▁children , ▁the ▁tum or ▁presents ▁as ▁a ▁pal p able ▁mass ▁in ▁the ▁sac rop el vic ▁region ▁compress ing ▁the ▁bl ad der ▁or ▁rect um . ▁These ▁pel vic ▁tum ors ▁have ▁a ▁greater ▁lik elihood ▁of ▁being ▁m align ant . ▁An ▁early ▁survey ▁found ▁that ▁the ▁rate ▁of ▁tum or ▁m align ancy ▁was ▁ 4 8 % ▁for ▁girls ▁and ▁ 6 7 % ▁for ▁boys ▁older ▁than ▁ 2 ▁months ▁at ▁the ▁time ▁of ▁sac roc oc cy ge al ▁tum or ▁diagn osis , ▁compared ▁with ▁a ▁m align ant ▁tum or ▁inc idence ▁of ▁ 7