Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says: When a she-camel is slaughtered, the fetus in its womb is counted as slaughtered too, if it is fully formed and its hair has grown; and if the fetus comes out of the womb alive, it is to be slaughtered so that the blood comes out of its body.
This is the correct version: it is mawquf (the Companion's own statement).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19493