Ovarian Hyperstimulation Syndrome (OHSS) is a potentially serious complication of fertility treatment.
Who gets it?
Any patient undergoing treatment with stimulation drugs during IVF is at some risk of developing ovarian hyperstimulation syndrome (OHSS).
Although we know that it is caused by the drugs we give you to simulate the ovaries, we do not know why only a small number of women develop these problems.
Who is most at risk?
Mild symptoms are common in women having IVF treatment. As many as one in three (33%) women develop mild OHSS. About one in 20 (5%) women develop moderate or severe OHSS.
The risk of OHSS is increased in women who:
- Have polycycstic ovaries
- Are under 30 years old
- Body Mass index (BMI) less than 19
- Very high ovarian reserve with AMH above 50 pmol/L.
- Have had OHSS previously
- Develop multiple follicles and high oestrogen levels during treatment
- Get pregnant, particularly if this is a multiple pregnancy (twins or more).
What causes it?
Fertility drugs stimulate the ovaries to produce many egg sacs (follicles). Sometimes there is an excessive response to fertility drugs and this causes OHSS.
Overstimulated ovaries enlarge and release chemicals into the bloodstream that make blood vessels leak fluid into the body. Fluid leaks into your abdomen and, in severe cases, into the space around the heart and lungs. OHSS can affect the kidneys, liver and lungs. A serious, but rare, complication is a blood clot (thrombosis). A very small number of deaths have been reported.
How safe is the treatment?
We will always discuss the risk peculiar to yourself and to your own treatment before starting.
The development of follicles is monitored using ultrasound scanning and hormone levels are assessed through blood test. It is very important for you to attend for all of your scan and blood test appointments during treatment. If during the treatment you do appear to be responding in such a way that we are concerned about the degree of risk we will discuss this with you.
You may choose to abandon the cycle of treatment at this stage, or to persist, or in some way to modify the treatment such as to reduce the risk. Rarely we may decide that the risk is too great and will advise that the treatment must be discontinued.