The possible window of implantation for embryos in the first frozen embryo transplantation cycle: A retrospective analysis.

OBJECTIVE: This study aimed to investigate the duration of progesterone (P) therapy on clinical pregnancy rates as measured by the window of implantation (WOI) in the first cycle of frozen embryo transplantation. METHODS: The study compared the pregnancy rates between 345 cleavage stage transfers and 348 blastocyte transfers of frozen embryos with modified natural cycles in patients from July 1, 2020, to November 30, 2020. Four different P durations were analyzed in the cleavage stage embryo transfer group, i.e., two, three, four, and five days. Five different P durations were analyzed in the blastocyst transfer group, i.e., three, four, five, six, and seven days. RESULTS: The baseline demographics and clinical characteristics of the cleavage stage embryos and blastocyst transfer groups were not comparable. The clinical pregnancy rates following the cleavage stage embryo transfer after two, three, four, and five-day P administration were 45.71%, 44.60%, 38.40%, and 30.43%, respectively (the difference among the subgroups was not significant). Following the blastocyst transfer, the clinical pregnancy rates after three, four, five, six, and seven-day P administration were 50.65%, 63.51%, 60.00%, 54.55%, and 61.54%, respectively (the difference among the subgroups was not significant). In contrast, these two transfer groups showed significantly different clinical pregnancy rates following four and five-day P exposure (P < 0.05). CONCLUSION: For cleavage-stage embryo transfer, the most effective WOI was found between days two and five of P administration. The effective WOI for blastocyst transfer was observed between days three and seven of P administrations.

Evaluation of the value of water retention service in the middle and upper reaches of Hunhe River based on SWAT Model.

The upper and middle reaches of the Hunhe River, with forest coverage rate up to 68%, is an important water source protection area in Liaoning Province. Based on the SWAT model and shadow engineering method, we aimed to estimate the function and service value of water retention in the upper and middle Hunhe River basin from 2000 to 2019, to analyze the spatial heterogeneity, and to provide a scientific basis for the ecological compensation and ecological restoration of the region. Our results showed that the function and service value of water retention in the upper and middle reaches of the Hunhe increased first, and then decreased from 2000 to 2019. The mean annual amount and service value of water retention were 2.46 billion m3 and 15.04 billion yuan, respectively. The spatial distribution of water conservation service functions in the study area was uneven. The areas of high water retention service value were mainly distributed in Qingyuan County and Xinbin County, while the low-value areas were located in municipal districts of Shenyang City. The value of water retention services was obviously different among the ecosystems, with water retention capacity per unit area of forests being much higher than that of grassland, farmland, and cities.