Received September 19, 2017
Accepted May 10, 2018

Objective: Coasting is a well-known strategy to decrease severity of Ovarian Hyperstimulation Syndrome (OHSS). The purpose of this study is to assess the effect of Coasting on blastocyst development and subsequent clinical outcome following exclusive blastocyst transfer. Methods: We conducted an observational cohort study of patients having blastocyst transfer following IVF/ICSI treatment. Patients undergoing IVF/ICSI cycles were included in the study. Patients at risk of OHSS were coasted. Outcome following exclusive blastocyst transfer was compared between coasted and non-coasted groups. The main outcome measures were the rate of blastocyst development and live birth rates in coasted and non-coasted cycles. Within coasted cycles, outcome was further analysed based on coasting duration and serum estradiol (E2) drop (difference between peak E2 and E2 on day of HCG). Results: A total of 166 coasted cycles and 656 non-coasted cycles had blastocyst transfer. Blastocyst development (45.97% vs. 48.6%) and live birth rates (45.18% vs. 43.44%) were not significantly different between coasted and non-coasted cycles. The overall clinical pregnancy (54.21% vs. 49.08%) and implantation rates (43.95% vs. 39.54%) following blastocyst transfer in coasted cycles were not significantly different from those of non-coasted cycles. Conclusion: Coasting duration up to 6 days and drop in serum E2 levels did not compromise blastocyst development, implantation, clinical pregnancy or live birth rates. We conclude that coasting with subsequent blastocyst transfer can be used as an effective strategy in patients at risk of OHSS with no detrimental effects on blastocyst development or live birth outcome.