Ovarian hyper stimulation syndrome, abbreviated as OHSS, occurs in some women who use fertility medications. These medications may cause swelling and fluid leakage from the ovaries if they overstimulate them, though the symptoms only occur after ovulation. Women who have certain conditions have a higher risk of developing OHSS. For example, women who have polycystic ovary syndrome, a condition in which women have multiple small cysts in their ovaries, have an increased risk of OHSS. Women who are younger than age 35 or a low body weight also have a higher risk. Other risk factors for OHSS include a large number of follicles and very high estrogen levels while in fertility treatment. Doctors diagnose OHSS based on the symptoms displayed. OHSS can also be detected with a vaginal ultrasound exam, which the doctor uses during the fertility treatment. The image created by the vaginal ultrasound will show if the ovaries are swollen, an indicator of OHSS.