P-626 Progesterone rescue is effective for clinical pregnancy outcome in women presenting low circulating progesterone levels at frozen embryo transfer day
Authors: Kim Y , Ryu E  K , Lee H , Hur Y  S , Lim K  S , Lee W  D 
Published: July 2024

Study question

Is subcutaneous progesterone (prolutex® 25mg daily) addition effective for clinical pregnancy outcome in women presenting low progesterone(P4) levels at frozen embryo transfer(FET) day?

Summary answer

Subcutaneous progesterone rescue improved ongoing pregnancy rate and clinical pregnancy rate in women with low P4 results at FET day.

What is known already

FET has been increased, because preimplantation genetic testing for aneuploidies is performed widely, and FET presents a significantly low risk of ovarian hyperstimulation syndrome.In FET, there is no established optimal protocol for preparing endometrium, but hormonal replacement therapy (HRT) is widely used due to its convenient schedule adjustment. HRT protocol induce anovulation, functioning corpus luteum is lacking and exogenous progesterone administration is very important. Therefore, women showing low P4 levels around FET day have lower pregnancy rate. However, there are currently no data on the effectiveness of progesterone rescue.

Study design, size, duration

Primary outcomes from a randomized cohort retrospective study investigating subcutaneous progesterone (prolutex® 25mg) daily addition for whom had low P4 levels (&lt;12ng/mL) at FET day. The study was conducted at one infertility center in Korea from January 2022 to December 2023 and pregnancy outcomes of FET transfers registered until Oct. 2023,. 194 patients fulfilled the inclusion criteria.

Participants/materials, setting, methods

One hundred ninety four women divided into two groups based on progesterone levels, with 12ng/ml as the threshold. Under 12ng/mL group were randomized to subgroup with and without addition of subcutaneous progesterone. In total 278 FET cycles, the effect of progesterone rescue on cumulative clinical pregnancy rate (CPR), Ongoing pregnancy rate (OPR) was reported as primary outcomes.

Main results and the role of chance

In total 278 cycles, there were 137 cycles with adequate serum P4 levels, while 141 cycles presented with low P4 levels in which randomly rescue subcutaneous progesterone administration added from next day of embryo transfer. When comparing the groups, there was no statistical difference in maternal age, BMI, smokers, duration of infertility, type of infertility, indication of in vitro fertilization(IVF), endometrial preparation method. In low P4 group, with and without subcutaneous progesterone addition subgroups included 51 and 90 cycles, retrospectively. CPR were 52.9% versus 35.6% (P = 0.044; chi-squared test) with a statistically significant higher rate of OPR in progesterone rescue group (45.1% versus 28.9%, p = 0.052). When comparing the group with adequate P4 levels and the group with low P4 levels without progesterone rescue, OPR were 18.2% versus 28.9% (p = 0.06, chi-squared test), CPR was significantly higher in low P4 levels group (23.4% versus 35.6%,p=0.046, chi-squared test). Adequate P4 level group had more IVF attempts (4.6 versus 2.2, p &lt; 0.001, chi-squared test). There is tendency to use more luteal phase support medication with repeated attempt (serum P4 concentration on ET day 39.3 ng/mL versus 8.7 ng/mL, p &lt; 0.001, t-test)

Limitations, reasons for caution

The main limitation of the study was retrospective, and had small sample size. A control group without progesterone rescue in low P4 levels did not receive any intervention.

Wider implications of the findings

The progesterone rescue for women presenting low P4 on FET day improved clinical outcome and excessively raising progesterone medication may have adverse effects. Therefore rather than using excessive progesterone administration from luteal support start day, progesterone rescue might be effective when low P4 levels presenting at FET day.

Trial registration number

not applicable