Given a passage with a context and an answer, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.

Context: Embryo transfer to a developed endometrium is an important prognostic factor in frozen-thawed embryo transfer cycle outcome. Vaginal estrogen, such as Vagifem vaginal tablets and Premarin vaginal cream, is a regimen used for the patients with refractive endometria.', 'Our objective was to compare the effects of Vagifem and Premarin on the endometrial thickness of the patients with refractive endometria.', 'In this randomized clinical trial, 30 patients with refractive endometria in frozen-thawed embryo transfer cycles received Vagifem vaginal tablets and 30 women received Premarin vaginal cream. Endometrial thickness was measured on the 14th day of drug administration.', 'Comparing the endometrial thicknesses of the two groups showed that the endometria of the Vagifem group was significantly thicker than that of the Premarin group (5.930.38 vs. 6.740.32; p<0.001).
Answer: Vagifem is superior to Premarin in induction of endometrial thickness in frozen-thawed embryo transfer cycles in the patients with refractive endometria.
Is vagifem superior to vaginal Premarin in induction of endometrial thickness in the frozen-thawed cycle patients with refractory endometria : A randomized clinical trial?