There is no selection pressure to make childbirth a pleasant experience. Instead, evolution made the early part, the intercourse, very pleasant.
Most animals have no problems giving birth, but a few have problems.
For human females, there is an evolutionary tradeoff between being able to give birth to a child with a huge head, and the ability to walk properly. You can’t walk properly if your hips are too wide. Evolution doesn’t make perfect, just good enough, which means that if enough women survives and produce living children it doesn’t matter much if a few dies. Especially, if without contraception, in the old days women often produced 10 children or more. That did make up for any losses, including the many children that died before reaching adulthood.
But humans are not the only animal that has birth problems. For example, hyenas have it even worse than human females. It’s an example where evolution really made a mess.
“The hyena females give birth through their narrow clitoris, and spotted hyena
cubs are the largest carnivoran young relative to their mothers’ weight. During parturition, the clitoris ruptures to facilitate the passage of the young, and may take weeks to heal.”
“Females giving birth for the first time die in 9-18% of the cases, and their cubs only survive in 25% of the cases. The birthing process itself can last up to 48 hours of excruciating pain