Ovarian Hyperstimulation Syndrome (OHSS): Prevention and Risk Factors
Ovarian Hyperstimulation Syndrome (OHSS) takes place when a female’s body over-responds to the hormone medications (notably injectable gonadotropins) used to stimulate egg development during a fertility treatment cycle.
Ovarian Hyperstimulation Syndrome (OHSS)
The “trigger” used for ovulation before the egg retrieval helps mature the eggs so they can be fertilized, but it also “luteinizes” the follicles in the ovaries. As the follicles turn into “corpora lutea” (plural for corpus luteum), many substances are produced that are usually designed to prepare the lining of the uterus for implantation. In a normal menstrual cycle, there is only one corpus luteum. When there are many corpora lutea, the substances produced can make the patient sick with ovarian hyperstimulation syndrome (OHSS). One central substance is VEGF (Vascular endothelial growth factor), a signaling protein that promotes the growth of new blood vessels. When it is secreted in large amounts, it makes the blood vessels “leaky”, and fluid seeps out of the vessels.
This can lead to accumulation of fluid in the abdomen and pelvis, in the peritoneal cavity. There can even be fluid under the lungs. Because fluid seeps out of the blood vessels, the blood becomes more concentrated, we say the patient is “hemoconcentrated”. This can increase the risk of blood clots.
How to Prevent OHSS
Fortunately, we now have 4 decades of experience with OHSS, and have found effective ways to prevent it. The most important elements in preventing OHSS are:
1) Identifying patients at risk
2) Choosing the doses for ovarian stimulation carefully
3) Monitoring patients closely with ultrasound and blood tests (E2 = estradiol).
In addition, the use of the “Lupron trigger” and the increased use of the “freeze-only“ strategy have made OHSS very rare. As a field, we are working on creating “OHSS-free clinics” by using the above tools, and a few others. Sometimes we recommend using a GnRH antagonist (such as Ganirelix) and / or a medication called Cabergoline after the egg retrieval to further decrease the risk in patients with lots of follicles / eggs retrieved.
Risk Factors for OHSS
The principal risk factors for OHSS are young age and high ovarian reserve (tested via AMH level and antral follicle count). Patients with polycystic ovarian syndrome (PCOS) are at especially high risk, especially young PCOS patients, given that PCOS is associated with extremely high ovarian reserve (very high follicle counts / high AMH levels).
During an IVF cycle, high numbers of developing follicles and high estradiol (E2) levels are risk factors for OHSS. Usually, your fertility specialist will make sure that the number of follicles and the E2 levels do not get too high, so that an adequate number of eggs can be retrieved while preventing OHSS.
To learn more about OHSS, click here!
Medical Disclaimer:
The information provided in this blog is intended for general informational purposes only and should not be considered as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your healthcare provider or qualified medical professional with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read in this blog.
