Quality or quantity? Pitfalls of assessing the effect of endometrial thickness on live birth rates

Letter to the Editor

VOLUME 118, ISSUE 2, P428


Baris Ata, M.D., M.Sc., Erkan Kalafat, M.D., M.Sc.


The study by Mahutte et al. (1) to identify “an optimal endometrial thickness” for embryo transfer has some limitations that could have led to inaccuracies. Although they reported that endometrial thickness was negatively correlated with patient age and positively correlated with parity, peak estradiol levels, numbers of oocytes at retrieval, and embryos available for transfer or cryopreservation in their dataset, none of their analyses were simultaneously adjusted for these confounding factors that also affect the live birth rate (1). Even the number of embryos transferred, which was significantly different between categories of endometrial thickness in fresh transfers, was not adjusted for (Supplemental Table 1 [available online] by Mahutte et al.) (1). Simultaneous adjustment for multiple confounders in a single model may have yielded different results, for example, the “surprising” relationship between thicker endometrial linings and live birth rates in fresh transfers may not have been observed (1).

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