Correctly timed coasting reduces the risk of ovarian hyperstimulation syndrome and gives good cycle outcome in an in vitro fertilization program.

One hundred and twelve severely overstimulated in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) patients were treated with coasting when estradiol concentration was > 3000 pg/ml and the leading follicles had attained > or = 18 mm in diameter. Gonadotropin withholding was offered to them as a promising method for the prevention of both cycle cancellation and complications associated with severe ovarian hyperstimulation syndrome (OHSS). The duration of prolonged coasting prior to human chorionic gonadotropin (hCG) administration ranged from 2 to 9 days (mean 3.5). hCG was administered when the serum estradiol dropped to < 3000 pg/ml and at least three growing follicles > or = 20 mm in diameter were present. Fertilization failure was noted in six couples and in another 10 cases freezing of all embryos was decided, therefore embryo transfer was performed on 96 patients. There were 31 clinical pregnancies (five twins) giving a pregnancy rate per patient and per embryo transfer of 30.4% and 32.3%, respectively, with an implantation rate of 18.1%. With regard to all 112 coasted patients, six developed moderate and two severe OHSS. This study shows that withholding gonadotropin administration in high-risk IVF patients results in a good cycle outcome and a very low risk of severe OHSS, and also demonstrates the importance of both the timing of coasting initiation and the timing of hCG administration.