Statistical and Power considerations: This is a Randomized Controlled Trial (RCT) with two study arms and panned crossover. Patients will be randomly assigned to Study group A or B according to a computer generated randomization table with 50:50 distributions. The study will test the null hypothesis that there is no difference in the transfer rates between the two groups. Transfer is only possible if the endometrial thickness reaches 7 mm or more. Order of treatment ab v ba will be added to the models as a separate factor and each phase will be analyzed as separate treatment strata.