One example is called egg-binding, also referred to as 'dystocia,' 'egg retention,' or 'post-ovulatory stasis' is common in many reptile species, including iguanas, snakes, and turtles. In many cases it is preventable with good nutrition and husbandry.
Egg-binding occurs when a female cannot pass the mature eggs formed in her reproductive system. In one survey it was found to occur in approximately 10% of the reptile population. It is reported more often in snakes and turtles, and less so in lizards. It is unclear if the difference is due to more snakes and turtles being bred, or if there actually is more dystocia in these species.