Having an OI is a very safe and simple fertility procedure. There is an increased chance of having a multiple pregnancy, such as twins, of around 2 to 5%. This is more likely if fertility injections have been used to encourage egg development and over five eggs grow. There is also a tiny (1/1000) chance of getting overstimulation of the ovaries OHSS. OHSS or ovarian hyperstimulation syndrome is a condition often requiring hospitalization, with many cysts on the ovaries and fluid in the abdomen.