Ovarian hyperstimulation syndrome (OHSS) is an iatrogenic phenomenon that results from stimulating the ovaries with gonadotropins. Normally this occurs during IVF stimulation regimens when doctors try to get several mature eggs to work with. In general, the more follicles that are recruited to grow, the higher the risk.
Mature follicles tend to secrete a number of hormones and growth factors (such as vascular endothelial growth factor or VEGF) that in the correct amounts have no ill effects. But when you have twenty follicles present as opposed to the traditional one, the concentrations of these chemicals increase greatly in the circulation and lead to the syndrome. Therefore, younger, more responsive women with good egg reserve are at the highest risk. Especially at risk are patients with polycystic ovarian syndrome (PCOS) because these women tend to have very many recruitable follicles lying dormant in their ovaries, and when stimulation is applied they all tend to grow together as a large group. Stimulating PCOS patients can be quite challenging as they tend to have an “all or none” response to their meds and getting a safe number is at times difficult to accomplish.
OHSS is a syndrome resulting from an excessive accumulation of fluid in the body’s potential spaces, around the abdominal organs (ascites in the peritoneal cavity), around the lungs (pleural effusions), or around the heart (pericardial effusion). The net effect is one of severe bloating, difficulty taking deep breaths, and general discomfort. This is accompanied by dehydration, as fluid leaves the circulatory system where it belongs and transudates into other locations. The dehydration can lead to blood clot formation and other symptoms such as decreased urine output, rapid heart rate (tachycardia), low blood pressure, severe thirst.
All good responders to meds tend to get a mild or moderate form of OHSS that self resolves after a few days. But when severe it can be life threatening. Thankfully such severe cases are rare and can nowadays be both prevented and ameliorated to a very large degree. Prevention can first and foremost be accomplished by simply cancelling the IVF cycle; although the stimulation meds set the patient up for OHSS it is the hCG trigger shot, or the hCG from any ensuing pregnancy, that really “lights the fuse” so to speak. In less risky circumstances, many doctors will finish the cycle out with hCG trigger shot and egg retrieval, but not transfer any embryos to avoid the prolonged hCG exposure that an immediate conception would create. Another technique to minimize OHSS risk is that of “coasting” in which the stim meds are stopped for several days during the regimen in an effort to allow the ovaries to “cool down” a bit before the hCG trigger shot is administered. It seems that even a coasting period for up to 3 days will have no ill effects on cycle outcome.
Another quite efficacious technique for minimizing OHSS is to trigger with a shot of Lupron rather than HCG; Lupron causes a natural LH surge that ripens nearly mature eggs but does not cause any prolonged ovarian stimulation the way a shot of hCG would do. This is due to the fact that natural LH has a very short half-life in the body but hCG does not. The one caveat for Lupron triggers is that it can’t be used in cycles already using Lupron as part of the IVF regimen.
Studies have also shown that using a dopamine agonist medication (like bromocriptine or dostinex) as well as a GnRH antagonist (like cetrotide or ganirelix) can minimize the symptoms of bloating if used after egg retrieval, and we tend to use both for patients at above average risk for OHSS – even if we have used any of the other aforementioned techniques – just to be safe.