Association between luteinizing hormone level decrease on the triggering day and pregnancy outcome for in vitro fertilization/intracytoplasmic sperm injection patients following gonadotropin-releasing hormone antagonist protocol: a retrospective cohort study

Objective: Optimal luteinizing hormone (LH) levels for in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) patients following the gonadotropin-releasing hormone (GnRH) antagonist protocol remain controversial. This study aimed to estimate the association between serum LH levels on the triggering day (LHLOT) and clinical pregnancy outcomes in IVF/ICSI patients following the GnRH antagonist protocol. Methods: We enrolled 4743 IVF/ICSI cycles using flexible or fixed GnRH antagonist protocols between January 2017 and June 2021. The patients were stratified into four groups according to the LHLOT quartiles (Q1-Q4). Each group was further divided into two subgroups according to the median basal LH/LHLOT. The main outcomes were clinical pregnancy, birth, and miscarriage rates. Secondary outcomes were oocyte yield, number of MII, fertilized oocytes (2PN), and high-quality embryos. Results: Serum LHLOT levels were negatively correlated with oocyte yield and the numbers of MII, 2PN, and high-quality embryos. Reproductive outcomes were compared among the different quartiles and subgroups. The absolute difference in the clinical pregnancy rates between the Q4 and Q1 groups was 6.4% (47.2% vs. 40.8%, P <0.05). Clinical pregnancy rates between the subgroups with basal LH/LHLOT >3.04 and <= 3.04 were 32.7% and 48.6% (P <0.01), respectively, in Q1. Within Q3, the clinical pregnancy rates between the subgroups with basal LH/LHLOT >2.14 and <= 2.14 were 50.2% and 41.9%, respectively (P <0.05). The greater the decrease in LH levels, the lower the oocyte maturation rate across all quartiles. Conclusions: According to the LHLOT quartiles, the Q1 of serum LHLOT <1.43 IU/L may result in a higher number of oocytes but reduced oocyte maturation and lower clinical pregnancy rates. A decrease in LH levels by approximately 2.14 to 3.04 times compared to basal LH levels may lead to higher clinical pregnancy rates in IVF/ICSI patients following the GnRH antagonist protocol.