Litwicka K, et al. - The present study was designed to determine whether in a modified natural cycle (modified-NC) for a frozen-thawed single euploid blastocyst transfer, a critical LH value, above which human chorionic gonadotropin (hCG) administration should be avoided, may be defined. Researchers observed that LH elevation ≥ 13 mIU/ml prior to hCG administration could have a negative effect on clinical pregnancy rates in modified-NC for single euploid blastocyst transfer. They recommended performing the LH determination routinely during follicular monitoring. As per findings, in the presence of LH level ≥ 13 mIU/ml, hCG administration should be avoided, and the embryo transfer should be planned only after spontaneous follicular rupture.