Effect of basal LH levels on pregnancy outcome after IVF/ICSI fresh embryo transfer in patients of different ages: a retrospective study.

BACKGROUND

The predictive value of basal luteinising hormone (LH) levels for pregnancy outcomes following in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) remains controversial, and whether this relationship differs by female age has not been fully established.

METHODS

A total of 1153 patients undergoing their first IVF/ICSI cycle with fresh embryo transfer at a university-affiliated reproductive medicine center between March 2020 and May 2022 were retrospectively analyzed. Patients were stratified by basal LH quartiles (<25th, 25th-75th, >75th) and age groups (<35, 35-37, and ≥38 years). Multivariable logistic regression was used to adjust for confounders, with candidate variables selected based on univariate analysis (P < 0.10) and clinical relevance. The primary outcomes were clinical pregnancy rate (CPR) and live birth rate (LBR).

RESULTS

The CPR and LBR declined progressively with increasing age (both P < 0.001). In patients aged <35 years, the >75th basal LH quartile was significantly associated with higher CPR (adjusted OR 1.885, 95% CI 1.267-2.803, P = 0.002) and higher LBR ((adjusted OR 1.702, 95% CI 1.146-2.529, P = 0.008) compared with the <25th quartile, after adjusting for age, body mass index, infertility cause, ovarian reserve markers, stimulation protocol, and embryo quality. Progesterone level on the day of human chorionic gonadotropin administration was negatively associated with CPR in this age group ((adjusted OR 0.603, 95% CI 0.402-0.906, P = 0.015). In patients aged 35-37 years, endometrial thickness was positively associated with both CPR and LBR, whereas no significant association between basal LH and pregnancy outcomes was observed. In patients aged ≥38 years, no significant association was found between basal LH and either CPR or LBR, and confidence intervals for basal LH estimates were notably wide in this subgroup.

CONCLUSION

Elevated basal serum LH levels are associated with higher CPR and LBR following fresh embryo transfer in patients aged <35 years, but this association is not observed in women aged ≥35 years.