Estimating the risks of ovarian hyperstimulation syndrome (OHSS): implications for egg donation for research.

This study aims to provide an estimate of women's risk of ovarian hyperstimulation syndrome (OHSS) when undergoing superovulation to donate eggs for research. This is an essential prerequisite for appropriate informed consent. In the absence of sufficiently large numbers of egg donors to assess the risk, comparative data was obtained from women undergoing the same superovulation protocol for in vitro fertilization (IVF) treatment. In this prospective study 339 women, who developed >/=20 follicles after superovulation in their first treatment cycle (total number of treatment cycles during the same period - 2417), were intensively monitored on five occasions, between human chorionic gonadotrophin and pregnancy test, according to our routine clinical protocol. Hospital admission was needed for 49 (14.5%) women, 13 (3.8%) needed intravenous fluids and 9 (2.7%) needed paracentesis. The admission rates were similar in pregnant and non-pregnant women (13.5% vs. 15%); the need for intravenous fluids and paracentesis were 3.2% vs. 2.3% and 6.3% vs. 2.3%, respectively. The peak increase in haematocrit occurred on Day 4 after hCG, and the mean day of hospital admission was Day 5. If an egg donor develops <20 follicles, she can be reassured that the risk of OHSS is very small (<0.1%). If >/=20 follicles develop, her risk of hospital admission due to OHSS is <15%. The absence of pregnancy in egg donors does not eliminate the risk of OHSS. Given the timescale of development of the haematological and biochemical abnormalities, egg donors who develop >/=20 follicles should be actively monitored for the first week after egg collection.