OHSS in IVF: how it is prevented and the signs to watch
Part of our guide to IVF treatment in Goa.
OHSS (ovarian hyperstimulation syndrome) happens when the ovaries over-respond to the egg-growth injections of IVF: they swell, and fluid leaks out of the blood vessels into the belly. Most cases are mild and settle on their own. A severe case is uncommon but serious, and most of the risk can be lowered before it starts: by spotting who is at risk, using gentle doses, choosing a safer trigger injection and, when the ovaries respond strongly, freezing all the embryos instead of transferring one in the same cycle.
Why does OHSS happen?
In a natural month one egg grows. In IVF the injections ask the ovaries to grow several eggs at once, each in its own fluid-filled follicle. When far more follicles grow than planned, the ovaries make large amounts of hormones that make blood vessels leaky. The final trigger for this is hCG, either from the trigger injection given before egg collection or, later, from a pregnancy itself. That is why OHSS shows up in the days after egg collection, and why a pregnancy can make it last longer.
Who is more likely to get OHSS?
- Women with PCOS, whose ovaries hold many small follicles waiting to grow.
- A high AMH result or a high antral follicle count on the first scan. Both are measured before the injections start, so the plan can be made gentle from day one.
- Younger women, who usually respond more strongly to the same dose.
- A woman who had OHSS, or a very strong response, in an earlier cycle.
- A cycle in which many follicles are growing and the hormone level in the blood rises fast.
None of these means OHSS will happen. They tell the team where extra care is needed.
How is the risk of OHSS lowered?
- Testing before the plan. AMH and a scan count of the resting follicles show how strongly the ovaries are likely to respond, so the starting dose is chosen for you, not from a standard chart.
- Gentle stimulation. The target is enough mature eggs for a fair chance, not the biggest count the ovaries can produce. Beyond a point, more eggs add risk without adding much to the chance of pregnancy.
- Scans and blood tests every two or three days. The doses are adjusted, raised or lowered, from what the follicles are actually doing.
- The antagonist protocol. This common IVF plan allows a different kind of trigger at the end of stimulation.
- An agonist trigger instead of hCG. When many follicles have grown, the eggs can be ripened with a GnRH agonist trigger injection, which sharply lowers the chance of early OHSS.
- Freezing all the embryos. If the response is strong, no embryo is transferred in that cycle. The embryos are frozen and placed later in a frozen embryo transfer, once the ovaries have settled.
- Stopping or changing a cycle when the response is far stronger than planned. It is disappointing, but it is the safe choice.
Why is freezing all the embryos often safer?
A pregnancy makes its own hCG, and that hCG can turn a mild OHSS into a severe one that lasts for weeks. When no embryo is transferred in the stimulated cycle, there is no pregnancy hCG in that month, so this late form of OHSS is largely avoided. The ovaries shrink back over the next period, and the frozen embryo is placed in a calmer cycle with a prepared lining. Freeze-all costs a few weeks of waiting. For a woman at high risk, it is usually the better trade. You can read how frozen embryos are kept on our page on embryo freezing.
Which OHSS signs are mild, and which are urgent?
Some bloating, a heavy or full feeling low in the belly, mild cramps and slight nausea are common after egg collection and usually ease within a week. These need rest and attention, not alarm.
Call the clinic at once, day or night, if you notice any of these:
- A belly that is swelling quickly or feels tight and hard
- Severe pain in the belly
- Vomiting, or being unable to keep fluids down
- Breathlessness, or difficulty lying flat
- Passing very little urine, or very dark urine
- Fast weight gain over one or two days
- Pain or swelling in one leg, or chest pain
Severe OHSS is treated in hospital, with fluids, close checks of the blood and urine, and sometimes draining the fluid from the belly. Early care makes a real difference, so never wait until the morning to call. If you cannot reach the clinic, go to the nearest hospital emergency department.
What helps at home after egg collection?
- Drink fluids through the day as you are advised, and include drinks with some salt and sugar, not plain water alone.
- Weigh yourself each morning and note roughly how much urine you pass, so you can tell the team if either changes.
- Rest, but keep moving gently around the house; do not stay in bed all day.
- Avoid heavy exercise and intercourse until the team says the ovaries have settled.
- Take only the medicines your doctor has prescribed. Do not take pain tablets on your own.
Does OHSS harm the eggs or the embryos?
Not as a rule. OHSS is about how the body reacts to the hormones, not about the quality of the eggs. Embryos frozen in a cycle where OHSS was a risk can be used later in the usual way. Many women whose ovaries respond strongly, including many with PCOS, go on to have a frozen transfer once the risk has passed.
For the whole IVF journey, from the first injection to the embryo transfer, see IVF treatment in Goa and IVF injections.
Questions about OHSS
What does OHSS mean in IVF?
OHSS stands for ovarian hyperstimulation syndrome. The egg-growth injections cause more follicles than intended, the ovaries enlarge and fluid shifts out of the blood vessels into the abdomen. Mild OHSS is common and settles; severe OHSS is uncommon and needs hospital care.
How is OHSS prevented?
The plan starts with an AMH test and a follicle count, then uses gentle doses with frequent scans. If many follicles grow, the antagonist protocol allows a GnRH agonist trigger in place of hCG, and the embryos can all be frozen for a later transfer.
Why are all the embryos frozen when OHSS is a risk?
A pregnancy makes hCG, which can make OHSS worse and longer. Without a transfer in that cycle there is no pregnancy hCG, so the ovaries settle and the embryo is placed later in a frozen transfer.
When does OHSS usually start?
Usually in the days after egg collection. If a fresh transfer leads to pregnancy, it can start or get worse about one to two weeks later, because of the pregnancy hormone.
Which symptoms need an urgent call?
A quickly swelling or tight belly, severe pain, vomiting, breathlessness, passing very little urine, fast weight gain, or pain and swelling in one leg. Call the clinic at once, day or night.
Does freezing all the embryos lower the chance of pregnancy?
For women at high risk of OHSS, a later frozen transfer is generally a safe and widely used choice. It mainly adds a few weeks of waiting.
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What you read here explains fertility care in general terms and cannot replace a consultation. Decisions about your own care should be made with a doctor who knows your history and has seen you. We do not carry out or offer sex determination of any kind, which is prohibited by law in India under the PCPNDT Act.