Prevention of severe ovarian hyperstimulation syndrome in IVF with or without ICSI and embryo transfer: a modified 'coasting' strategy based on ultrasound for identification of high-risk patients.

Ovarian hyperstimulation syndrome (OHSS) can be a severe and potentially life-threatening complication of ovarian stimulation for IVF. Coasting or withholding gonadotrophin stimulation relies on frequent estimation of serum oestradiol to identify patients at risk. A modified coasting protocol was developed in which identification of patients at risk of severe OHSS was based on ultrasound monitoring. Serum oestradiol concentrations were measured only in patients with >20 follicles on ultrasound (high risk). If serum oestradiol concentrations were <3000 pmol/l, the gonadotrophin dose was maintained; if concentrations were >/=3000 pmol/l but <13200 pmol/l and >/=25% of the follicles had a diameter of >/=13 mm, the gonadotrophin dose was halved; and if serum oestradiol concentrations were >/=13 200 pmol/l and >/=25% of the follicles had a diameter of >/=15 mm, patients were coasted. In the latter group, human chorionic gonadotrophin (HCG) 10000 IU was administered when at least three follicles had a diameter of >/=18 mm and serum oestradiol concentrations were <10000 pmol/l. Over a 10 month period, serum oestradiol concentrations were measured in 123 out of 580 cycles (24%) and in 50 cycles, gonadotrophins were withheld. Overall, moderate OHSS occurred in three patients (0.7%) and severe OHSS in one patient (0.2%). The pregnancy rates in the cycles where the gonadotrophin dose was reduced or withheld were 39.6 and 40% per cycle respectively; corresponding implantation rates were 30.7 and 25.6%. It is concluded that the modified coasting strategy is associated with a low risk of moderate and severe OHSS to a minimum without compromising pregnancy rates. Identification of patients at risk by ultrasound reduces the number of serum oestradiol measurements and thus inconvenience to patients as well as costs and workload.