Table 2.

Characteristics of the studies included in the systematic review.

Authors & Year	Type of the Study	Main Aim	Population of Nulliparous LNG-IUS Users	Type of LNG-IUS	Observation/ Follow-Up Time
Pakarinen et al. 1996 [41]	Randomized prospective	To compare the efficacy, safety and acceptability of LNG-IUS situated in the cervical canal or uterine cavity	N = 145 69 LNG-IUS intracervical 76 LNG-IUS intrauterine	20 µg/24 h	1 year
Suhonen et al. 2004 [45]	Randomized prospective	To compare the safety and acceptability of LNG-IUS and OCs in young nulliparous women	N = 94 Median age: 21; Range: 18–25	Mirena 20 µg/24 h; Total content: 52 mg Size: 32 × 32 mm	1 year
Wildemeersch et al. 2005 [51]	Open prospective noncomparative	To evaluate the ease of insertion, contraceptive performance and the safety of LNG-IUS Femilis	N = 92 Mean age: 29 Range: 16–50	Femilis Slim 20 µg/24 h Total content: 40 mg Size: 30 × 24 mm	1 year
Römer et al. 2009 [42]	Cross-sectional	To identify the characteristics and experiences of women using LNG-IUS	~ 694 8% of 8680-whole study group	Mirena 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	20% used IUS < 1 year, 16% 1–2 years; 15% 2–3 years; 14% 3–4 years; 13% 4–5 years; 18% > 5 years; 3% no data
Wildemeersch et al. 2009 UPDATE ON: Wildemeersch et al. 2005 [50]	Open prospectivenoncomparative	To provide an update on the performance of LNG-IUS Femilis in parous and nulliparous women	N = 112 Mean age: 29 Range: 17–48	Femilis20 µg/24 hTotal content: 60 mgSize: 30 × 28 mm	5 years
Bahamondes et al. 2011 [32]	Retrospectivecohort	To evaluate the ease of insertion and clinical performance of LNG-IUS in nulligravidas for up to 1 year after insertion	N = 158 Mean age: 30	Mirena 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	1 year
Marions et al. 2011 [39]	Non-interventional cohort	To gain knowledge about the insertion and the use of LNG-IUS in nulliparous women	N = 224Median age: 20	Mirena 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	Follow-ups: 1st 2–5 weeks (N = 137) 2nd 12–26 weeks (N = 197) 3rd 30–124 weeks (optional) (N = 134)
Armitage et al. 2013 [31]	Observational prospective	To follow 100 women attending for fitting LNG-IUS at a single urban general practice serving students	N = 97 Age range: 18–38	Mirena 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	1 year
Madden et al. 2014 [38]	Secondary analysis of Contraceptive CHOICE Project [53]	To investigate if young age and nulliparity were associated with the expulsion of LNG or Cu-IUS	N = 1690	20 µg/24 h	1 year
Savasi et al. 2014 [43]	Retrospective	To assess complication rates with the use of LNG-IUS in adolescents with developmental disabilities	N = 54	Mirena 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	Follow-up after the insertion of IUD ranged from 0 to 51 months (15 months on average)
Zhao et al. 2014 [52]	Prospective	To analyze experiences and the levels of satisfaction with Mirena among Chinese women	N = 77	Mirena 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	Follow ups: 1st 3–4 months 2nd 1 year
Abraham et al. 2015 [30]	Secondary analysis of Contraceptive CHOICE Project [53]	To assess the relationship among young age, nulliparity and the continuation of LARC methods	N = 1456	Not specified	Follow ups: 1st 1 year 2nd 2 years
Kaislasuo et al. 2015 [37]	Prospective cohort	To assess if small uterine cavity size was associated with bleeding problems or pain in nulligravid women using IUD	N = 111	Mirena 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	1 year
Gemzell-Danielsson et al. 2015 [35]	Randomized prospective	To evaluate if the outcomes of LNG-IUS were affected by parity, age or BMI	N = 1130 Age range: 18–35	49%-LNG-IUS 8 µg/24 h Total content: 13.5 mg 51%-LNG-IUS 13 µg/24 h Total content: 19.5 mg Both size: 28 × 30 mm	3 years
Eisenberg et al. 2015 [34]	Partially randomized prospective	To assess 3-year data on the efficacy and safety of 52 mg LNG-IUS	N = 1011 at enrollment Mean age: 25 Range: 16–45	Liletta 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	3 years
Mejia et al. 2016 [40]	Secondary analysis of Contraceptive CHOICE Project [53]	To evaluate the effect of baseline bleeding patterns on the rates of amenorrhea during the use of 52 mg LNG-IUS	N = 515	Total content: 52 mg	1 year
Hall et al. 2016 [36]	Observational	To follow college students who chose IUD and assess the insertion, use, continuation, and satisfaction	N = 88 Aged 18–30	Mirena 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	1 year
Wildemeersch et al. 2017 [49]	Observational prospective	To report on the contraceptive performance of LNG-IUS after 5 years of use	N = 117 Mean age: 27 Range: 15–47	Femilis 20 µg/24 h Total content: 60 mg Size: 30 × 28 mm	5 years (N = 114)
Darney et al. 2018 [33]	Prospective cohort	To evaluate amenorrhea rates and predictors during the 1st year of LNG-IUS use	N = 822	Liletta 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	1 year
Schreiber et al. 2018 [44]	Prospective	To evaluate bleeding patterns for Liletta using the WHO Belsey definitions	N = 982	Liletta 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	First 90 days (N = 982) Second 90 days (N = 949) Last 90 days of year 1 (N = 866) Last 90 days of year 2 (N = 711) Last 90 days of year 3 (N = 568)
Vaitsiakhovich et al. 2018 [48]	Cross design analysis of randomized and observational data	To evaluate the discontinuation rate of LNG-IUS in real-life setting	N = 50	Mirena 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	2 years
Teal et al. 2019 UPDATE ON: Eisenberg et al. 2015 [46]	Partially randomizedprospective	To re-assess the efficacy and safety of 52 mg LNG-IUS after 5 years of use (the continuation of Eisenberg et al. 2015)	N = 1011 Mean age: 25 Range: 16–45	Liletta 20 µg/24 h Total content: 52 mg Size: 32 × 32 mm	5 years (N = 986)
Teunissen et al. 2019 [47]	Retrospective cohort	To investigate differences in continuation rates between the contraceptive and therapeutic use of LNG-IUS	N = 379	Total content: 52 mg	Minimum 5 years

Abbreviations: BMI: body mass index; Cu-IUS: Copper-releasing intrauterine system; IUS: intrauterine system; LNG-IUS: levonorgestrel releasing intrauterine system; OC: oral contraceptives; WHO: World Health Organization; LARC: long-acting reversible contraception; IUD: intrauterine devices.