PurposeTo determine whether the cycle regimens that are used for endometrial preparation are associated with the birthweight (BW) after assisted reproductive technology (ART) using frozen‐thawed embryo transfer (FET).MethodsThe BW of singletons who were born by ART using FET was compared retrospectively, according to whether a FET was conducted in a hormone replacement therapy cycle (HRT, n = 403) or an ovulatory cycle (OVL, n = 117). The BW after timed intercourse (NAT, n = 162) also was investigated.ResultsThere were no significant differences in the age of the mothers, percentage of primiparas, gestational periods, Body Mass Index, and sex ratio between the HRT and OVL cycles. The average BW from HRT was significantly greater than that of OVL. The BW from HRT was also greater, compared with NAT, while statistical significance was not achieved between OVL and NAT. The putative factors affecting the BW, such as ovarian stimulation protocols, endometrial thickness, and the stage and quality of embryos, could not explain the difference in the BW between the HRT and OVL cycles.ConclusionAn increased BW from ART using FET seems to be ascribable to conditions of the endometrium, but not cryopreservation procedures per se, which might provide a mechanistic framework for understanding heavier neonates who are born by FET.

Ta2O5–xEr2O3 (TE) films were produced by a sol-gel method and a dip-coating technique with heat treatment at 600–1000 °C. Their powders were also prepared from the same sol. The Er3+ fluorescence property of the TE films containing various contents of Er3+ was measured as a function of the heat-treatment temperature. In crystallized films, the Er3+ fluorescence was observed because water-related residues (Ta–OH and H2O) and carbon-related residues (–CH3, –CH2–, –(C ⁼ O)–, and C≡C–H) were removed from the films. It is shown from infrared absorption spectroscopy that Ta–O− and Ta ⁼ O structures dissolve the Er3+ ions selectively and play a role in dispersing the Er3+. The strongest Er3+ fluorescence is observed in the TE film with 2 mol% of Er2O3 because of its highest ability to disperse the Er3+ ions.

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