RELATIONSHIP BETWEEN TEMPORAL CHANGES OF ENDOMETRIAL BLOOD FLOW IMPEDANCE IN A NATURAL AND HORMONE REPLACEMENT CYCLE AND PREDICTION OF PREGNANCY DURING VITRIFIED-WARMED EMBRYO TRANSFER

Abstract

Frozen-thawed embryo transfer (ET) is performed in a natural or hormone replacement therapy (HRT) cycle for endometrial preparations. However, how to determine which endometrial preparation method is suitable for the individual is unknown.This study was to examine the relationship between the temporal changes in endometrial blood flow impedance during natural and HRT cycles and clinical outcomes in vitrified-warmed ET. A single-center retrospective observational cohort study. This study was approved by the institutional review board of the Fukushima Medical University. This study included a total of 60 women, 28 with natural and 32 with HRT cycles, who underwent vitrified-warmed ET. Uterine radial artery resistance index (RA-RI) was measured during the natural and HRT cycles at the early follicular phase, days of the human chorionic gonadotropin trigger during a natural cycle or start of progesterone administration during the HRT cycle, and the day of ET. The association between the RA-RI at the different measurement point and the pregnancy were examined in the natural and HRT cycles by univariate analysis and multivariate logistic analysis. Receiver-operating characteristic analysis was used to determine the cut-off value of the RI with respect to pregnancy in natural and HRT cycles. The area under the curves (AUC) and their 95% confidence intervals (CI) were calculated. The clinical pregnancy rates of the natural and HRT cycles were 32.1% and 34.4%, respectively. In the univariate analysis, the RA-RI at the early follicular phase was significantly lower in the pregnant group than that in the non-pregnant group in the natural but not HRT cycle (P=0.04). In the multivariate logistic analysis, the RA-RI at the early follicular phase was an independent predictive factor for pregnancy in the natural but not HRT cycle (P=0.02). The odds ratio for pregnancy was 0.7 (95% CI, 0.52–0.95) when the levels of RA-RI at the early follicular phase was increased by 0.01 in the natural cycle. With the natural cycle, the area under the receiver-operating characteristic curves for the RA-RI at the early follicular phase with a threshold of 0.68 was 0.75 (95% CI, 0.57–0.93). The positive predictive and negative predictive values were 0.53 (95% CI, 0.37–0.59) and 0.92 (0.74–0.99), respectively. With the natural cycle, the RA-RI at the early follicular phase was associated with pregnancy, and this might have a potential in predicting pregnancy in vitrified-warmed ET cycles. Our findings suggest that RA-RI at the early follicular phase might be an effective and useful tool in choosing natural or HRT cycles for vitrified-warmed ET. This provides a clue to the individualization of the choice of an endometrial preparation method during the frozen-thawed ET.