Tearing
Unless you have experienced trauma in this area before (picture below), the skin of the perineal area and the internal tissues is relatively flexible.
Obviously, the flexibility and elasticity of the perineal area varies from one individual to another, except that the female body is suited to giving birth and therefore, nature has indeed anticipated that a baby will pass through this region.
As you can see, the perineum is not a fragile part of the anatomy.
And yet, it is common for this region to be damaged during childbirth.