It is worth quoting Rivero and Tschudi:
“We ourselves have observed the same fact [of the absence of signs of artificial pressure – IG] in many mummies of children of tender age, who, although they had cloths about them, were yet without any vestige or appearance of pressure of the cranium.
More still: the same formation of the head presents itself in children yet unborn; and of this truth we have had convincing proof in the sight of a foetus, enclosed in the womb of a mummy of a pregnant woman, which we found in a cave of Huichay, two leagues from Tarma, and which is, at this moment, in our collection [my emphasis – IG].