Received February 12, 2020
Accepted August 20, 2020

Objective: To evaluate the effects of three different estrogen used for endometrium preparation on pregnancy rate, as well as hormone profile on day 5 frozen embryo transfer (FET) cycles. Methods: Retrospective, observational study. Setting: A tertiary teaching and research private reproductive medicine center. Patient(s): Ninety patients who were undergoing endometrium preparation for day 5 frozen embryo transfer cycle (FET). Intervention(s): Women were divided in three groups according to administration route of estrogen (E2) : oral (Primogyna), transdermal patches (Estradott), or transdermal gel (Oestrogel Pump). These administration routines of estrogen are equivalent to 6 mg of estradiol daily. All women received 600mg of vaginal progesterone (P) per day (Utrogestan) in luteal phase support. Blood samples were drawn on starting P day, as well as beta hCG day for E2 and P measurements. Main Outcome Measure(s): Clinical pregnancy rates (PR). Results: Patient features in the three groups were comparable. No significant differences were found concerning implantation rate, clinical PR, miscarriage rate, multiple-pregnancy rate, or E2 and P levels on starting P day and on beta hCG day. Conclusions: In FET cycles with oral (Primogyna) or transdermal patches (Estradott), or transdermal gel (Oestrogel Pump) , no significant difference was observed on pregnancy rates.