Giving birth to her child is the single most natural thing a woman can do, where as being sliced open and having her infant cut out of her may as well be an alien abduction nightmare made real. Everything from hormonal balance to her subconscious state is completely fucked sideways by a c-section preventing the infant from passing through her birth canal, which denies that primordial bonding from properly taking place in almost every instance of the procedure. Ask a woman who has had a c section and, more often than not, they will quietly admit that there is a niggling little feeling in the back of their head that tells them their child never really felt like "their's".
TLDR: it causes the big mommy energy to fizzle out.