Objective

Frozen-thawed embryo transfer (FET) has been successfully performed in natural cycles following spontaneous ovulation and in artificially hormone replacement cycles. The absence of further hormonal therapy in natural cycle protocols is attractive to women. Patient monitoring prior to FET in natural cycle consists of serial hormone and vaginal sonography testing until detection of ovulation. Alternatively, timing of ovulation could be determined by vaginal sonography only. The purpose of this study is to compare cycle outcomes of FET with simple monitoring (vaginal sonography only) and intensive monitoring (hormone testing and vaginal sonography) in natural cycle.

Design

Retrospective cohort study.

Materials and Methods

We retrospectively reviewed 774 FET cycles using natural cycle protocol from July 2011 to December 2014. Timing of ovulation was determined by vaginal sonography only (Simple group) or vaginal sonography and hormone study (Intensive group). Frozen-thawed day 3 embryo transfer was done after 3 days of ovulation. We compared cycle outcomes of the two groups.

Results

In each group, age, the number of transferred embryos and percentage of top quality embryos did not show significant differences. Number of visiting days was similar between two groups. There were no significant differences between two groups in the clinical pregnancy rate [ Intensive group :35.7%(187/524) vs. Simple group:34.4%(86/250), P=0.787], spontaneous abortion rate [8.0%(15/187) vs. 5.8%(5/86), P=0.689] and ongoing pregnancy rate [32.8%(172/524) vs. 32.4%(81/250), P=0.907].

Conclusions

Intensive monitoring with serial hormone and vaginal sonography testing might predict more exact timing of ovulation as compared with simple monitoring by sonography only. However, pregnancy rate was not increased with intensive monitoring in this study. It is probably because implantation window usually exceed 1 day. Therefore, by simple monitoring with sonography only patients could avoid blood sampling and reach a similar outcome of intensive monitoring. FET with simple monitoring in natural cycle could be a good option to patients who want to avoid blood sampling and favor more patient-friendly method.