The ISMAAR proposal on terminology for ovarian stimulation for IVF.

IVF is performed with oocytes collected in natural and stimulated cycles. Different approaches to ovarian stimulation have been employed worldwide. Following the introduction of GnRH antagonists and strategies to reduce multiple births such as single embryo transfer, there is a genuine scientific interest in the revival of natural cycle and mild approaches to ovarian stimulation in IVF. Recent evidence suggests that application of natural and mild IVF is patient-centred, aimed at reducing the cost of treatment, patient discomfort and multiple pregnancies. However, there seems to be no consistency in the terminology used for definitions and protocols for ovarian stimulation in IVF cycles. Following the recent International Society for Mild Approaches in Assisted Reproduction (ISMAAR) meeting and communication with interested international experts, this article has recommended revised definitions and terminology for natural cycle IVF and different protocols used in ovarian stimulation for IVF. It is proposed that these terms are adopted internationally in order to achieve a consistency in clinical practice, research publications and communication with patients.