A Caesarean section was a medical procedure in which an incision was made through a mother's abdomen to deliver a baby, sometimes in an urgent emergency situation.
In 2259 in the alternate reality, Doctor Leonard McCoy told Carol Marcus that he had once performed a Caesarean section on a female Gorn, delivering her of octuplets. According to him, they could bite. (Star Trek Into Darkness)
This is a reference to events mentioned by McCoy in the 2013 Star Trek video game, although the incident he refers to was never seen, only related to Kirk over the comms. While landed on the Lymax planet, Sulu stuns a pregnant female Gorn, necessitating the operation. He further clarifies that they "almost bit my hand off!", prompting laughter from Kirk.
In 2367, Beverly Crusher referred to the spaceborne entity named Junior's birth as a Caesarean section. The baby was too weak to break through its dead mother's shell on its own, so using a narrow ship's phaser beam as a scalpel, an incision was made into the dead creature, just big enough for Junior to break free on its own. (TNG: "Galaxy's Child")