P-429 Measuring serum progesterone levels on the day of a fresh blastocyst transfer is debatable as there is no evidence for correlation with ongoing pregnancy results
Authors: Rottiers A  S , De Roo C , Vandierendonck F , Heindryckx B , Tilleman K , De Croo I , Vanden Meerschaut F , Dhaenens L , Stoop D 
Published: July 2024

Abstract

Study question
Does serum progesterone (P4) level on the day of a fresh blastocyst transfer relate to ongoing pregnancy rate (OPR)?

Summary answer
OPR after a fresh single blastocyst transfer seems not to be associated with serum P4 level on the day of transfer.

What is known already
Several studies have suggested an optimal serum P4 threshold for embryo transfers in frozen embryo transfer cycles. However, for fresh embryo transfers, data are scarce and conflicting.

Study design, size, duration
A retrospective single-center cohort study was performed on 598 complete data cycles, retained out of 631 consecutive fresh single blastocyst transfer cycles. Data were collected from patients undergoing a fresh IVF/ICSI cycle with autologous oocytes at a tertiary fertility center between June 2022 and August 2023.

Participants/materials, setting, methods
A total of 482 unique patients underwent one or more single fresh blastocyst transfers using micronized vaginal progesterone (MVP) 800mg BID for luteal phase support starting day after oocyte retrieval. Serum P4 levels were determined on day of transfer. The primary endpoint was OPR, positive hCG-test and early pregnancy loss (EPL) were secondary endpoints. Unadjusted and adjusted generalized estimating equations (GEE) assessed P4 level association with the endpoints, using an exchangeable working correlation matrix.

Main results and the role of chance
No association was identified between P4 levels on day of transfer and OPR after accounting for maternal age, blastocyst quality, P4 and estradiol level at last ultrasound, BMI and endometrial thickness. Data were grouped according to 10/50/90 and 25/50/75 percentiles, resulting in groups &lt; = or &gt; 27ng/ml and &lt; = or &gt; 40ng/ml, with omission of 90th and 75th percentile groups due to right-skewed distribution.
With serum P4 levels higher than 40ng/ml, the probability of a positive hCG-test significantly increased (OR 1.79, CI 1.11-2.91; p = 0.018). No significant difference was observed in patients with serum P4 &lt; = or &gt; 27ng/ml (OR 1.23, CI 0.66-2.30; p = 0.506).
Regarding OPR, no significant differences were observed when comparing patients with serum P4 &lt; = or &gt; 27/ng/ml or &lt; = or &gt; 40ng/ml (OR 0.88, CI 0.42-18.85; p = 0.736 and OR 1.41, CI 0.83-2.37; p = 0.203, respectively). Moreover, EPL did not significantly differ between serum P4 level groups (OR 1.93, CI 0.61-6.13; p = 0.265 and OR 1.2, CI 0.51-2.84; p = 0.674).
Age (p &lt; 0.001) and embryo quality (p &lt; 0.001) are significantly related with OPR. Additionally, late follicular progesterone levels and OPR are significantly associated (OR 2.39, CI 1.16-4.95 in patients with P4 &lt; = or &gt; 27/ng/ml and OR 2.21, CI 1.07-4.55 in patients with &lt; =40ng/ml and &gt;40ng/ml).

Limitations, reasons for caution
Limitations include the retrospective design and the lack of live birth outcome data. Progesterone levels exceeding 60 ng/ml were not further analyzed to their precise value but grouped as 60 plus which did not allow to identify potential detrimental effects of very high P4 levels on treatment outcome.

Wider implications of the findings
Our data suggest that measuring P4 on the day of a single blastocyst transfer with MVP luteal phase support may not be indicative of OPR or the risk of EPL. This raises questions regarding the necessity for routine P4 measurements as well as the development of rescue strategies.

Trial registration number
ONZ-2023-0628