Withholding gonadotrophin administration (coasting) may prevent severe ovarian hyperstimulation syndrome (OHSS). To ascertain the effectiveness of this protection a cohort of 252 consecutive in-vitro fertilization (IVF) or IVF with intracytoplasmic sperm injection (ICSI) cycles was studied. Twenty women with exaggerated response were treated with coasting. Despite coasting, four patients developed severe OHSS requiring hospitalization. Two of these four patients also required paracentesis. Multiple regression analysis in coasting cycles revealed severe OHSS was related to youth, number of oocytes retrieved and serum oestradiol prior to human chorionic gonadotrophin (HCG). Risk of developing severe OHSS was multifactorial and not necessarily prevented by withholding gonadotrophin.