The impact of the trigger day progesterone, luteinizing hormone and their interaction on live birth rates in GnRH antagonist cycles

Aim: This study aims to assess the impacts of various trigger day progesterone (P₄) and luteinizing hormone (LH) levels on live birth rates (LBRs) in fresh in vitro fertilization (IVF) cycles, considering their elevation from stimulation and premature luteinization.

Methods: This retrospective cohort study included the first ovarian stimulation cycles with GnRH antagonist protocol of 1253 patients who underwent intracytoplasmic sperm injection and fresh embryo transfer at a tertiary clinic's IVF center between 2010 and 2016. Participants were divided into four groups based on trigger day serum P₄ and LH levels, using the 90th percentile thresholds for P₄ (1.7 ng/mL) and LH (5.2 IU/L). The primary outcome measure was LBR.

Results: The LBRs observed in the respective groups were as follows: P₄ < 1.7 ng/mL and LH <5.2 IU/L (21.3%, 214/1005); P₄ < 1.7 ng/mL and LH ≥5.2 IU/L (19.1%, 22/115); P₄ ≥ 1.7 ng/mL and LH <5.2 IU/L (19.3%, 23/119); and P₄ ≥ 1.7 ng/mL and LH ≥5.2 IU/L (28.6%, 4/14). There were no statistically significant differences between the groups (p = 0.782). Additionally, a multivariate generalized additive model, adjusted for female age, body mass index, infertility duration, number of embryos transferred, and embryo transfer day, found that the interaction between LH and P₄ levels did not significantly predict LBRs (p = 0.533). However, univariate analysis identified an optimal trigger day P₄ range between 0.58 and 1.69 ng/mL for achieving higher LBRs, demonstrating a non-linear relationship. Furthermore, total FSH and LH dosages during stimulation had a statistically significant combined effect on trigger day P₄ levels (p = <0.001), with the addition of LH leading to lower P₄ levels compared to cycles stimulated with recombinant FSH alone.

Conclusions: The relationship and interaction between trigger day LH and P₄ levels do not significantly influence LBRs, as variations in LH do not alter the effect of P₄, suggesting that the impact of P₄ elevation on LBRs is independent of its cause, whether from ovarian stimulation or premature luteinization.