Ovarian hyperstimulation syndrome (or OHSS) is a condition caused by the ovulation-inducing drugs taken during the early stages of IVF treatment. Most cases of OHSS are very mild. In fact, approximately 1/3 of women undergoing IVF will experience these symptoms before they disappear after a few days. Less than 10% of women will suffer from moderate to serious OHSS.

IVF Drugs

A number of IVF drugs cause OHSS by doing exactly what they are meant to do - stimulating the ovaries into producing many mature eggs all at once. The problem in OHSS is that the ovaries have been stimulated to such an extent that they begin to leak fluid into the ovarian follicles. The follicles are the fluid-filled sacs in the ovaries, in which the eggs develop. When the ovaries leak fluid in this way, they become swollen. This causes a range of problems, the mildest of which are tenderness and abdominal pain, while the most serious include respiratory difficulty and thrombosis (blood clots).

The drugs that can cause these problems are:

FSH (follicle stimulating hormone) - this drug makes the follicles develop and nurture the eggs inside them.

LH (luteinizing hormone) - this drug triggers the follicles to release the eggs inside them.

hMG (human menopausal gonadotropin) - this drug functions in much the same way as FSH and LH

hCG (human chorionic gonadotropin) - this drug has the same function as LH.

Mild OHSS Symptoms

Mild OHSS symptoms will usually go away after about a week. If they last for more than a week, then they will usually be classed as moderate symptoms. If you do actually get pregnant after a round of IVF during which you have developed OHSS, there's a chance that you could be dealing with symptoms for several weeks.

These symptoms usually begin around 10 days after the injection is given to trigger the release of the eggs from the ovaries.

Mild symptoms include:

- Mild nausea with some vomiting

- Pain and discomfort in the abdominal area, with some tenderness around the area of the ovaries

- Bloating

- Constipation or diarrhea, or both, intermittently

- Passing dark, concentrated urine

Tell Your Doctor!

It's absolutely essential that you bring OHSS symptoms to your doctor's attention. Many women going through IVF have a lot invested in the process. They fear that if they tell their doctors about the OHSS symptoms, the IVF treatment will be stopped and they will lose out on their last chance to have a baby. While this is very understandable, it's a dangerous attitude to take. Mild OHSS symptoms can often be handled without stopping IVF. But if symptoms are not treated or monitored, or they may develop into severe OHSS - then a woman's life could possibly be in danger.


An option for women whose ovaries don't react well to IVF drugs is the possibility of freezing eggs or freezing embryos resulting from one cycle of IVF, for use in further IVF treatments. Check our resources on egg and embryo freezing in the IVF procedure section for more information.

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