P-649 Circadian serum progesterone variations on the day of frozen embryo transfer in artificially prepared cycles

Abstract

Abstract Study question What is the intra-day variation of serum progesterone related to vaginal progesterone administration on the day of frozen embryo transfer (FET) in an artificial cycle? Summary answer We observed a statistically significant intra-day variation of serum progesterone (P) levels on the day of FET in artificially prepared cycles (AC). What is known already The use of FET cycles has increased enormously. In an attempt to further optimize pregnancy outcomes after FET, recent studies have focused on the importance of correct serum luteal P levels in both natural and AC-FET cycles. Despite the different cut-off values proposed to define low serum P, it is generally accepted that lower serum P values(<8.8 ng/ml) around the day of FET are associated with lower live birth rates and higher miscarriage rates. However, a single luteal serum P measurement can be misleading given the diurnal variation and the impact of patient characteristics such as age, BMI, parity, ethnicity. Study design, size, duration A prospective cohort study was conducted at a tertiary university-based hospital encompassing twenty-two patients undergoing a single blastocyst transfer in an AC from August to December 2022. Sample size calculation was performed using a paired t-test resulting in twenty-two patients required to detect a difference of 15% between the first and the last daily progesterone value with a false-positive rate of 5%(two-sided),a power of 80%,assuming a standard deviation of change in the outcome of 0.250. Participants/materials, setting, methods Patients with a normal BMI,aged between 18 and 40 years old, were included. Endometrial preparation was achieved by administering estradiol valerate(6 mg/day) until an adequate endometrial thickness was reached. Consecutively, micronized vaginal progesterone(MVP, 800 mg/die) was started five days prior to blastocyst transfer. P levels were evaluated on the day of FET at 08:00h, 12:00h, 16:00h, and 20:00h. The first and last blood samples were collected just before the intake of MVP,at 8:00h and 20:00h. Main results and the role of chance Mean age of the study population was 33.95 ± 3.98 years and BMI 23.10 ± 1.95 kg/m2. Basal FSH was 7.84 ± 2.31 IU/L and estradiol concentration at 8:00h on the day of FET was 206.04 ± 93.32 ng/L. Mean P values at 08:00h, 12:00h, 16:00h and 20:00h were 11.72 ± 4.99 µg/L, 13.59 ± 6.33 µg/L, 10.23 ± 3.81 µg/L and 9.28 ± 3.09 µg/L,respectively. Statistically significant differences in P values were observed between measurements performed at 08:00h and 20:00h (p = 0,007), 8:00h and 12:00h(p < 0,001), 12:00h and 16:00h (p < 0,001), and 16:00h and 20:00h (p = 0,004). The proportion of patients encountering low P values, defined as P < 8.8 ng/ml, was 27,3% at 8:00h, 13,6% at 12:00h, 40,9% at 16:00h, and 36,4% at 20:00h. Moreover, the difference in patients with normal P values (> 8.8 ng/ml) was statistically significant between samples performed at 8:00h and 12:00h and 12:00h and 16:00h (p = 0.009 and p = 0.01 respectively). No difference was observed in normal P values between 16:00h and 20:00h(p = 0.3) and 8:00h and 20:00h(p = 0,07). Additionally, no association was found either between age and BMI and the first progesterone evaluation of the day, neither between these parameters and the difference in P levels between 8:00h and 20:00h. Limitations, reasons for caution The strict inclusion criteria applied in this study could potentially imply a bias when extrapolating the results to a wider infertile population undergoing AC-FET cycles. A confirmation of the findings in larger prospective studies including a more heterogeneous patient population is recommended. Wider implications of the findings The results of this study highlight the importance of a standardized procedure for the timing of progesterone measurements, partly taken into account the last MVP intake. This is especially important when clinical actions, such as additional P supplementation, are considered when low or high P values are encountered. Trial registration number not applicable