Hormonal Contraception and Endometrial Thickness in IVF/ICSI Cycles: A Multicentre Historical Cohort Study

Area of Science:

• Reproductive Medicine
• Gynecology
• Endocrinology

Background:

• Endometrial thickness (EMT) is a critical factor for successful in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) implantation.
• Previous contraceptive use can potentially influence endometrial receptivity and thickness.
• Understanding the impact of different contraceptive methods on EMT is crucial for optimizing fertility treatments.

Purpose of the Study:

• To investigate the association between prior use of the levonorgestrel intrauterine system (LNG-IUS) and endometrial thickness (EMT).
• To compare EMT in women undergoing IVF/ICSI cycles based on their history of LNG-IUS use versus other contraceptive methods.
• To determine if duration of LNG-IUS use affects endometrial growth.

Main Methods:

• A multicentre historical cohort study involving 12,786 women undergoing IVF/ICSI between 2000 and 2021.
• Analysis of endometrial thickness (EMT) measurements (≥7 mm vs. <7 mm).
• Mixed-effects logistic regression adjusted for age, BMI, smoking, education, FSH dose, and fertility clinic, comparing LNG-IUS users with users of combined oral contraceptive pills (OCPs), progestin-only pills (POPs), or no/other contraception.

Main Results:

• Previous use of OCPs, POPs, and no/other contraception was associated with significantly higher odds of achieving an EMT of ≥7 mm compared to LNG-IUS use.
• All duration categories of prior LNG-IUS use demonstrated statistically significantly lower odds of achieving an EMT ≥7 mm compared to no/other contraception.
• The findings indicate a potential negative impact of LNG-IUS on endometrial development relevant to IVF/ICSI outcomes.

Conclusions:

• Prior utilization of the levonorgestrel intrauterine system (LNG-IUS) is associated with diminished endometrial growth.
• This reduced endometrial thickness may have implications for implantation rates in women undergoing assisted reproductive technologies.
• Further research is warranted to explore the mechanisms behind LNG-IUS's effect on the endometrium in the context of IVF/ICSI.