When I started to write about ovarian hyperstimulation syndrome (OHSS), I began to write in great detail about the pathophysiology and management of OHSS. But most patients just want to know the details in understandable terminology. Here, I answer some common questions about OHSS.
What is OHSS?
Ovarian hyperstimulation syndrome, also known as OHSS, is “an exaggerated response to ovulation induction therapy.” In other words, OHSS can occur when one takes medications to grow more than one egg on the ovaries. According to the Practice Committee of the American Society for Reproductive Medicine, “The syndrome is a broad spectrum of clinical manifestations, from mild illness needing only careful observation to severe disease requiring hospitalization and intensive care.” The committee also states, “OHSS is a self-limiting disorder that resolves spontaneously within several days, but may persist for longer durations particularly in conception cycles.”
Why does OHSS occur?
When the eggs are harvested from overstimulated ovaries, “leaky vessels” may result. This can lead to leakage of fluid from the blood stream into the abdominal and lung cavities. The movement of fluid from the blood stream to areas usually devoid of fluid is what leads to the symptoms of OHSS. The severity of the disease is determined by the amount of fluid that accumulates. For instance, the more fluid that accumulates the more severe the case of OHSS. Unfortunately, modern science has not discovered the exact reasons why this occurs after egg retrieval. However, a lot of research is underway to find out.
What are the symptoms of OHSS?
Ovarian hyperstimulation syndrome symptoms can range from mild to severe. The symptoms depend on the severity of the OHSS.
About a third of all cases of OHSS after in vitro fertilization (IVF) are mild and include some of the following symptoms:
- Lower abdominal discomfort
- Mild nausea
- Abdominal distention
Very rarely, in about 0.1 to 0.2 percent of cases, women with severe OHSS experience one or more of the following symptoms:
- Rapid weight gain
- Tense ascites (This is the development of a lot of fluid in the abdomen that could make the abdomen protrude out. Some women may look as though they are far along in a pregnancy).
- Breathing difficulty
- Progressive decrease in urination and kidney function
- Abnormal lab levels such as low sodium or high potassium
- Low blood pressure
Life threatening complications of OHSS can include:
- Renal failure
- Respiratory distress
- Hemorrhage from ovarian rupture
- Blood clots
When does OHSS occur?
Typically OHSS does not develop until after ovulation or egg retrieval in assisted reproductive technology (ART) cycles. Symptoms can occur early after the retrieval and before transfer. Symptoms can also occur later, such as after the transfer has occurred. If conception occurs, the symptoms can last longer.
Who is at risk for OHSS?
Women at higher risk for OHSS are those who undergo egg recruitment with injectable medications called gonadotropins that also have one or more of the following characteristics:
- Young age
- Low body weight
- Polycystic ovary syndrome (PCOS)
- Higher doses of exogenous gonadotropins
- High absolute or rapidly rising serum estradiol levels
- Previous episodes of OHSS
Risk also increases with the number of oocytes retrieved in ART cycles (such as taking injectable medications combined with intrauterine insemination or IVF). Pregnancy increases the likelihood, duration, and severity of OHSS symptoms. Once the symptoms resolve after several days, OHSS will not return. However, after experiencing OHSS, one’s risk for OHSS is greater in a future ART cycle.
Source: The Practice Committee of the American Society for Reproductive Medicine. Fertility and Sterility Vol. 80, No. 5, 11/2003, p.1309 – 1314.
Dr. Lowell T. Ku, M.D. is an award winning and leading Reproductive Endocrinology and Infertility specialist at Dallas IVF, one the nation’s premiere infertility centers. Dr. Ku clarifies the many confusing terms used in the world of Infertility using straightforward explanations.