JBRA Assist. Reprod. 2025;29(Suppl 1):52-52
POSTER PRESENTATION
doi: 10.5935/1518-0557.20250106
1BIOS - Centro de Medicina Reprodutiva do Ceará
Objective: Frozen embryo transfer is a common practice in in vitro fertilization (IVF), allowing the preservation of viable embryos for future transfers. This technique can be performed in natural cycles or artificial cycles, each with its advantages and disadvantages. The natural cycle involves transferring the embryo during a regular menstrual cycle, while the artificial cycle uses hormones to prepare the endometrium to receive the embryo. This study aims to compare pregnancy rates and obstetric outcomes after frozen embryo transfers in both types of cycles.
Methods: A retrospective study was carried out with 569 patients who underwent frozen embryo transfer between February 2022 and September 2024 in an assisted reproduction clinic. The patients were divided into two groups: Group A, transfer of thawed embryos in a natural cycle, and Group B, transfer of thawed embryos in an artificial cycle. Clinical pregnancy rates were assessed, defined as the presence of a fetal heartbeat on ultrasound. In addition, obstetric outcomes were analyzed, including rates of miscarriage, ectopic pregnancy, and pregnancy complications.
Results: The results showed that the clinical pregnancy rate was significantly higher in Group A (natural cycle) with 65.74% compared to Group B (artificial cycle), which had a rate of 61.26%. Furthermore, the spontaneous abortion rate was lower in Group A, at 4.8%, compared to 10.1% in Group B. Gestational complications, such as ectopic pregnancy and pre-eclampsia, were similar between the groups. The observed differences can be attributed to the more favorable hormonal environment in the natural cycle, where ovulation and endometrial preparation occur physiologically, resulting in better endometrial receptivity. Previous studies also indicate that the administration of exogenous hormones during the artificial cycle can interfere with the quality of the endometrium, compromising the chances of implantation and embryonic development. Furthermore, patients on natural cycles may have a better hormonal adjustment, with a natural peak of progesterone and estrogen, which may favor embryo implantation. These findings are consistent with the literature, which suggests that natural cycles offer an environment closer to physiological, potentially benefiting reproductive outcomes.
Conclusion: Frozen embryo transfers performed in natural cycles have demonstrated higher clinical pregnancy rates and lower miscarriage rates compared to artificial cycles. The choice of method must take into account the individual characteristics of each patient, aiming to optimize reproductive results.