Definition of Ovarian hyperstimulation syndrome:

Ovarian hyperstimulation syndrome (OHSS) is a complication occasionally seen in women who take certain fertility medicines that stimulate egg production.

See also: Infertility

Causes, incidence, and risk factors:

Normally, a woman produces one egg per month. Some women undergoing fertility treatments are given medicines to help normalize egg development or increase egg production.

However, if the drugs stimulate the ovaries too much, the ovaries can suddenly become very swollen and fluid can leak into the belly and chest area. This is called ovarian hyperstimulation syndrome (OHSS). OHSS occurs only after the eggs are released from the ovary (ovulation).

You may be more likely to get OHSS if your doctor gives you an injection of a hormone called human chorionic gonadotropin (hCG) to help trigger ovulation. You may have an even greater risk of this syndrome if you receive more than one dose of hCG after ovulation and if you become pregnant during this cycle. OHSS rarely, if ever, occurs in women who only take fertility medicines by mouth.

OHSS affects up to 10% of women who go through in vitro fertilization. In most cases the condition is mild, but some women get a severe and dangerous form of OHSS.

Additional risk factors for OHSS include:

• Age younger than 35
• Very high estrogen level while undergoing fertility treatments
• Polycystic ovarian syndrome