Extended coasting duration exerts a negative impact on IVF cycle outcome due to premature luteinization.

Coasting, or withholding gonadotrophin administration while maintaining gonadotrophin-releasing hormone analogue until oestradiol drops to a safe concentration, is an alternative approach to prevent ovarian hyperstimulation syndrome (OHSS) in high responder patients. However, the length of this procedure has not been precisely studied. This paper is a retrospective study of 132 patients who showed a high response (oestradiol > 4500 pg/ml and/or more than 20 follicles > 17 mm) to ovarian stimulation and were coasted due to their high risk of developing OHSS, and evaluated the impact of the duration of coasting on IVF cycle outcome. Additionally, serum LH and progesterone concentrations were studied to investigate whether premature luteinization was present in these cycles and whether it might be related to coasting duration. A significant decrease in implantation rate was found when coasting was required for more than 4 days, together with a trend towards a higher cancellation rate. Premature luteinization was significantly elevated in women undergoing coasting compared with control women (34 versus 15.6%, P < 0.05). In the majority of patients who showed premature luteinization, coasting lasted >/=3 days. To conclude, prolonged coasting may affect the endometrium, anticipating the implantation window. These data may explain why some women undergoing extended coasting show a lower implantation rate compared with controls.