The most worrisome complication of IVF is that of ovarian hyperstimulation syndrome (OHSS), because of superovulation.
The cause of "ovarian hyperstimulation syndrome" is that superovulated ovaries contain many follicles which are loaded with estrogen. After ovulation, a huge amount of estrogen-rich fluid is poured directly out of the enlarged and fragile ovaries into the abdominal cavity. This fluid also contains chemicals like kallikrein-kinin and VEGF (vascular endothelial growth factor), which then coat the lining of the abdominal cavity (called the peritoneum) and cause it to become very permeable (leaky). Fluid (serum) literally pours out of bloodstream into the peritoneal cavity because of the "leakiness" of the abdominal cavity's lining. The ovaries balloon in size, the abdomen swells, and some women may get lightheaded with relatively low blood pressure, or dizzy because of the decreased blood volume. Many women going through IVF treatment will have mild degrees of ovarian hyperstimulation with a little bit of lower abdominal swelling, discomfort, and dizziness. This does not require hospitalization, just bed rest at home. It is only the rare, severe cases that require hospitalization. The occasional patient today who develops severe hyperstimulation must go into the hospital, have intravenous fluids for several days, and wait for her ovaries to reduce in size and for her body to readjust. Some patients may even need to be admitted into an intensive care unit for monitoring and observation, since this can be life-threatening.
Because hyperstimulation occurs more commonly in patients with PCOD, which is not very common in the West, the experience which clinics in the UK and the USA have in dealing with this problem is very limited. Since PCOD is quite common in India, we have extensive experience in preventing OHSS, and have not needed to hospitalise a patient for this complication for the last 10 years. This is because we use a special technique during egg collection with a double lumen needle, which allows us to remove all the granulosa cells from each follicle at the time of egg retrieval, by flushing each follicle meticulously. Since these cells are the ones responsible for producing the chemicals which cause OHSS, by removing them we reduce the risk of our patients getting OHSS dramatically !
At one time , OHSS was a very dangerous condition only because it was not fully understood. The best way to deal with OHSS is to prevent it, by using the technique we have developed.
Even if OHSS does develop, doctors can treat it by putting a small "paracentesis" catheter into the abdomen and draining all of this fluid. The patient is made much more comfortable, she can breathe more easily, and by getting rid of this estrogen irritation, fluid leakage into the abdomen slows down dramatically. Thus, even in the very rare cases of severe hyperstimulation syndrome, knowledgeable treatment makes the likelihood of any dangerous outcome very remote.
Interestingly, the worst cases of hyperstimulation syndrome occur when a woman becomes pregnant. This is because her placenta is making HCG and stimulating the ovaries to continue to pour out large amounts of estrogen-rich fluid. So although it is a very unpleasant side effect to endure, hyperstimulation syndrome often means good news.
If you grow too many follicles (more than 25) , or if your estradiol level is very high, many clinics in the West are forced to cancel the IVF cycle, because of their fear of your developing ovarian hyperstimulation syndrome. ( Remember that hyperstimulation cannot occur unless ovulation takes place. Thus, if the doctor withholds the HCG injection, there is no risk of developing hyperstimulation. ) However, this means that your cycle gets cancelled and the treatment is wasted. Because of the special technique we use, we do not need to cancel these cycles, and can go ahead with egg collection, thus saving our patients a lot of money, and maximising their chances of conceiving. In other clinics , doctors salvage these cycles by collecting all the eggs and freezing all the embryos. Since the embryos are not transferred, the risk of hyperstimulation is reduced; and the frozen embryos can then be transferred in a future cycle.