biostudies-literatureUnknown132(11)Michaelsen MPThe Clinical Surgery and Cancer Treatment Research Fund<h4>Objective</h4>To study the association between previous use of levonorgestrel intrauterine system (LNG-IUS) and endometrial thickness (EMT) in women undergoing in vitro fertilisation (IVF)/intracytoplasmic sperm injection (ICSI) cycles.<h4>Design</h4>Multicentre historical cohort study.<h4>Setting</h4>Eight Danish public and private fertility clinics.<h4>Population</h4>12786 women aged 18-46 years contributing with an EMT measurement from 22 464 different IVF/ICSI treatment cycles between 2000 and 2021.<h4>Methods</h4>Exposure was previous use of LNG-IUS, combined oral contraceptive pills (OCPs), progeste-only pills (POPs), no/other contraception or combined, cumulated use of contraception when more contraceptives had been used during the inclusion period. Further, ever use of LNG-IUS was categorised into 0-3 years, > 3-6 years, > 6-9 years and > 9 years. Mixed effect logistic regression adjusted for age, BMI, smoking, educational level, total FSH dose and fertility clinic was used.<h4>Main outcome measure (s)</h4>EMT (< 7 mm ≥ 7 mm).<h4>Results</h4>Statistically significantly higher odds of EMT ≥ 7 mm were found for OCPs [odds ratio (OR) 3.53 (95% confidence interval (95% CI) 1.29-9.65)], POPs [OR 6.43, (95% CI 1.45-28.63)] and no/other contraception [OR 6.67, (95% CI 2.37-18.74]) relative to LNG-IUS in IVF/ICSI cycles. Further, all duration categories of ever use of LNG-IUS were associated with statistically significantly lower odds of obtaining an EMT ≥ 7 mm compared to no/other contraception.<h4>Conclusions</h4>In this study, previous use of LNG-IUS was associated with decreased endometrial growth in women undergoing IVF/ICSI.BJOG : an international journal of obstetrics and gynaecology1681-1688https://www.ebi.ac.uk/biostudies/studies/S-EPMC12411652biostudies-literatureHormonal Contraception and Endometrial Thickness in IVF/ICSI Cycles: A Multicentre Historical Cohort Study.PMC12411652Gabrielsen AVPovlsen BBNielsen LCBentzen JGElers JTang-Pedersen MGrondahl MLSkals RGPoulsen MMichaelsen MPTroest BKesmodel USfalseHormonal Contraception and Endometrial Thickness in IVF/ICSI Cycles: A Multicentre Historical Cohort Study.<h4>Objective</h4>To study the association between previous use of levonorgestrel intrauterine system (LNG-IUS) and endometrial thickness (EMT) in women undergoing in vitro fertilisation (IVF)/intracytoplasmic sperm injection (ICSI) cycles.<h4>Design</h4>Multicentre historical cohort study.<h4>Setting</h4>Eight Danish public and private fertility clinics.<h4>Population</h4>12786 women aged 18-46 years contributing with an EMT measurement from 22 464 different IVF/ICSI treatment cycles between 2000 and 2021.<h4>Methods</h4>Exposure was previous use of LNG-IUS, combined oral contraceptive pills (OCPs), progeste-only pills (POPs), no/other contraception or combined, cumulated use of contraception when more contraceptives had been used during the inclusion period. Further, ever use of LNG-IUS was categorised into 0-3 years, > 3-6 years, > 6-9 years and > 9 years. Mixed effect logistic regression adjusted for age, BMI, smoking, educational level, total FSH dose and fertility clinic was used.<h4>Main outcome measure (s)</h4>EMT (< 7 mm ≥ 7 mm).<h4>Results</h4>Statistically significantly higher odds of EMT ≥ 7 mm were found for OCPs [odds ratio (OR) 3.53 (95% confidence interval (95% CI) 1.29-9.65)], POPs [OR 6.43, (95% CI 1.45-28.63)] and no/other contraception [OR 6.67, (95% CI 2.37-18.74]) relative to LNG-IUS in IVF/ICSI cycles. Further, all duration categories of ever use of LNG-IUS were associated with statistically significantly lower odds of obtaining an EMT ≥ 7 mm compared to no/other contraception.<h4>Conclusions</h4>In this study, previous use of LNG-IUS was associated with decreased endometrial growth in women undergoing IVF/ICSI.2025-01-01T00:00:00Z2025 Oct2026-05-29T20:12:50.359Z2026-04-08T05:56:22.088ZS-EPMC124116524066577910.1111/1471-0528.18295