Impact of the type of endometrial oestrogen preparation for frozen-thawed embryo (vaginal or transdermal) on perinatal outcomes in an artificial cycle

Effect of estrogen exposure on pregnancy outcomes in artificial frozen-thawed embryo transfer cycles

In contemporary times, the employment of vitrification freezing technology has led to the widespread adoption of frozen-thawed embryo transfer (FET) worldwide. Meanwhile, hormone replacement therapy (HRT) is a crucial protocol for priming the endometrium during FET cycles. Estrogen is required in HRT cycles for the induction of progesterone receptors and to promote endometrial thickness. However, there is no universal consensus on the treatment duration, dosage regimen, administration route, and target serum estrogen levels. Therefore, this study aimed to offer a comprehensive review of these topics. A shorter duration of estrogen exposure may elevate the risk of early miscarriage, while prolonged exposure to estrogen does not seem to confer advantages to general population and may be attempted in individuals with thin endometrium. Moreover, excessive estrogen levels on the day of progesterone administration may be associated with higher miscarriage rates and lower live birth rates (LBR). To offer more comprehensive guidance for clinical practice, extensive and prospective studies involving a large sample size are warranted to determine the optimal concentration and duration of estrogen exposure.

Preparation of the endometrium for frozen embryo transfer: an update on clinical practices

Over the past decade, the application of frozen-thawed embryo transfer treatment cycles has increased substantially. Hormone replacement therapy and the natural cycle are two popular methods for preparing the endometrium. Hormone replacement therapy is now used at the discretion of the doctors because it is easy to coordinate the timing of embryo thawing and transfer with the schedules of the in-vitro fertilization lab, the treating doctors, and the patient. However, current results suggest that establishing a pregnancy in the absence of a corpus luteum as a result of anovulation may pose significant maternal and fetal risks. Therefore, a 'back to nature' approach that advocates an expanded use of natural cycle FET in ovulatory women has been suggested. Currently, there is increasing interest in how the method of endometrial preparation may influence frozen embryo transfer outcomes specifically, especially when it comes to details such as different types of ovulation monitoring and different luteal support in natural cycles, and the ideal exogenous hormone administration route as well as the endocrine monitoring in hormone replacement cycles. In addition to improving implantation rates and ensuring the safety of the fetus, addressing these points will allow for individualized endometrial preparation, also as few cycles as possible would be canceled.

Analysis of Relevant Factors Affecting the Pregnancy Rate of Frozen-Thawed Embryo Transfer Cycle

Objective

The aim of this study is to explore the relevant factors affecting the pregnancy rate of frozen-thawed embryo transfer cycle.

Methods

The clinical data of 931 patients who underwent artificial cycle preparation for endometrial FET from April 2017 to November 2020 in the reproductive center of our hospital were retrospectively analyzed.

Results

According to the pregnancy situation, the patients were divided into 450 cases of pregnancy and 481 cases of biochemical pregnancy. The univariate analysis of FET biochemical pregnancy showed that there were statistically significant differences between pregnancy and biochemical pregnancy in terms of years of infertility, age, endometrial thickness, P level, E2/P, and the number of high-quality embryos (P < 0.05). Multivariate analysis of pregnancy showed that age <30 years was a protective factor for biochemical pregnancy and endometrial thickness <8 mm and E2/P < 0.3 were risk factors (P < 0.05).

Conclusion

The regulation of endometrial thickness and E2/P serves as the key of treatment for patients undergoing FET using artificial cycle preparation for endometrial transfer, and it contributes to improve the pregnancy rate; also, the patient's age is an important indicator influencing the pregnancy rate.