Participants randomised to treatment arm will undergo an endometrial biopsy procedure using Pipelle endometrial sampler (Pipelle de Cornier, Laboratoire CCD, Paris, France) or Wallace/ Wallach endometrial sampler as an alternative device on cycle day LH+7 to LH+9 of the cycle directly preceding commencement of down-regulation prior to IVF or ICSI treatment. The endometrial sampling will be repeated a maximum of four times (all during the same appointment on day LH+7 to LH+9 of menstrual cycle) to assure a sufficient sample is obtained. If following the first two attempts, the endometrial sample is sufficient, procedure will be deemed complete. The Pipelle sampler will be introduced up to the uterine fundus (based on clinical touch technique and ultrasound measurements), and attempts will be made to obtain samples from all four walls of the endometrial cavity.