STUDY QUESTION

What are the plasma concentrations of dydrogesterone (DYD) and its metabolite, 20α-dihydrodydrogesterone (DHD), measured on day of embryo transfer (ET) in programmed anovulatory frozen embryo transfer (FET) cycles using 10 mg per os ter-in-die (tid) oral DYD, and what is the association of DYD and DHD levels with ongoing pregnancy rate?

SUMMARY ANSWER

DYD and DHD plasma levels reach steady state by Day 3 of intake, are strongly correlated and vary considerably between and within individual subjects, women in the lowest quarter of DYD or DHD levels on day of FET have a reduced chance of an ongoing pregnancy.

WHAT IS KNOWN ALREADY

DYD is an oral, systemic alternative to vaginal progesterone for luteal phase support. The DYD and DHD level necessary to sustain implantation, when no endogenous progesterone is present, remains unknown. While DYD is widely used in fresh IVF cycles, circulating concentrations of DYD and DHD and inter- and intraindividual variation of plasma levels versus successful treatment have never been explored as measurement of DYD and DHD is currently only feasible by high-sensitivity chromatographic techniques such as liquid chromatography/tandem mass spectroscopy (LC-MS/MS).

STUDY DESIGN, SIZE, DURATION: Prospective, clinical cohort study (May 2018-November 2020) (NCT03507673); university IVF-center; women (n = 217) undergoing a programmed FET cycle with 2 mg oral estradiol (tid) and, for luteal support, 10 mg oral DYD (tid); main inclusion criteria: absence of ovulatory follicle and low serum progesterone on Days 12-15 of estradiol intake; serum and plasma samples were taken on day of FET and stored at -80°C for later analysis by LC-MS/MS; in 56 patients, two or more FET cycles in the same protocol were performed.

PARTICIPANTS/MATERIALS, SETTING, METHODS: Women undergoing FET on Day 2 or Day 3 (D2, D3, cleavage) or Day 5 (D5, blastocyst) of embryonic development had blood sampling on the 3rd, 4th or 6th day of 10 mg (tid) DYD oral intake, respectively. The patient population was stratified by DYD and DHD plasma levels by percentiles (≤25th versus >25th) separately by day of ET. Ongoing pregnancy rates (a viable pregnancy at >10th gestational week) were compared between ≤25th percentile versus >25th percentile for DYD and DHD levels (adjusted for day of ET). Known predictors of outcome were screened for their effects in addition to DYD, while DYD was considered as log-concentration or dichotomized at the lower quartile. Repeated cycles were analyzed assuming some correlation between them for a given individual, namely by generalized estimating equations for prediction and generalized mixed models for an estimate of the variance component.

MAIN RESULTS AND THE ROLE OF CHANCE

After exclusion of patients with 'escape ovulation' (n = 14, 6%), detected by the presence of progesterone in serum on day of ET, and patients with no results from LC-MS/MS analysis (n = 5), n = 41 observations for cleavage stage ETs and n = 157 for blastocyst transfers were analyzed. Median (quartiles) of plasma levels of DYD and DHD were 1.36 ng/ml (0.738 to 2.17 ng/ml) and 34.0 ng/ml (19.85 to 51.65 ng/ml) on Day 2 or 3 and 1.04 ng/ml (0.707 to 1.62 ng/ml) and 30.0 ng/ml (20.8 to 43.3 ng/ml) on Day 5, respectively, suggesting that steady-state is reached already on Day 3 of intake. DHD plasma levels very weakly associated with body weight and BMI (R2 < 0.05), DYD levels with body weight, but not BMI. Levels of DYD and DHD were strongly correlated (correlation coefficients 0.936 for D2/3 and 0.892 for D5, respectively). The 25th percentile of DYD and DHD levels were 0.71 ng/ml and 20.675 ng/ml on day of ET. The ongoing pregnancy rate was significantly reduced in patients in the lower quarter of DYD or DHD levels: ≤25th percentile DYD or DHD 3/49 (6%) and 4/49 (8%) versus >25th percentile DYD or DHD 42/149 (28%) and 41/149 (27%) (unadjusted difference -22% (CI: -31% to -10%) and -19% (CI: -29% to -7%), adjusted difference -22%, 95% CI: -32 to -12, P < 0.0001).

LIMITATIONS, REASONS FOR CAUTION: Some inter- and intraindividual variations in DYD levels could be attributed to differences in time between last 10 mg DYD intake and blood sampling, as well as concomitant food intake, neither of which were registered in this study. Ninety percent of subjects were European-Caucasian and DYD/DHD blood concentrations should be replicated in other and larger populations.

WIDER IMPLICATIONS OF THE FINDINGS

Daily 10 mg DYD (tid) in an artificial FET cycle is potentially a suboptimal dose for a proportion of the population. Measurement of DYD or DHD levels could be used interchangeably for future studies. The pharmacokinetics of oral DYD and associated reproductive pharmacodynamics need further study.

STUDY FUNDING/COMPETING INTEREST(S): The trial was financed by university funds, except for the cost for plasma and serum sample handling, storage and shipment, as well as the liquid chromatography-mass spectrometry (LC-MS/MS) analysis of DYD, DHD and progesterone, which was financially supported by Abbott Products Operations AG (Allschwil, Switzerland). Abbott Products Operations AG had no influence on the study protocol, study conduct, data analysis or data interpretation. K.N. has received honoraria and/or non-financial support (e.g. travel cost compensation) from Ferring, Gedeon-Richter, Merck and MSD. A.M. has no competing interests. R.V. has no competing interests. M.D. has received honoraria and/or non-financial support from Ferring and Merck. A.S.-M. has no competing interests. T.K.E. has received honoraria and/or non-financial support from Roche, Novartis, Pfizer, Aristo Pharma, Merck. G.G. has received honoraria and/or non-financial support (e.g. travel cost compensation) from Abbott, Ferring, Gedeon Richter, Guerbet, Merck, Organon, MSD, ObsEva, PregLem, ReprodWissen GmbH, Vifor and Cooper.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT03507673.