***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND The study was conducted to examine the hypotheses that adolescent and young adult women who perceived they are susceptible to pregnancy when birth control is not used are less likely to practice unsafe sex , discontinue oral contraception ( OC ) and become pregnant during a 12-month follow-up period . STUDY DESIGN We conducted secondary analyses using data collected for a r and omized controlled trial on OC adherence among 1155 low-income women 16 - 24 years of age .  Demographics , lifestyle variables , perceived susceptibility to pregnancy assessed at baseline , and data on OC and condom use and pregnancy status collected during 12 months of follow-up were used for the analyses . RESULTS Overall , 62.3 % of women accurately understood the risks of pregnancy without using any birth control method . However , perceived susceptibility was not associated with OC continuation [ odds ratio ( OR ) 0.94 , 95 % confidence interval ( CI ) 0.79 - 1.11 ] , condom use at last sexual intercourse ( OR 1.02 , 95 % CI 0.84 - 1.24 ) , dual method use ( OR 1.17 , 95 % CI 0.92 - 1.48 ) and subsequent pregnancy ( hazards ratio 1.08 , 95 % CI 0.77 - 1.49 ) during the 12-month follow-up period . CONCLUSIONS Perceived susceptibility to pregnancy , an important component of the health belief model , does not seem to have any impact on use of birth control methods , safer sex or rate of subsequent pregnancy among low-income adolescent and young adult women This 1-year r and omized study was carried out at family-planning clinics of two university hospitals to compare the safety and acceptability of a levonorgestrel-releasing intrauterine system ( LNG IUS ) and oral contraceptives ( OCs ) in young nulliparous women . The study population consisted of 200 women aged 18 - 25 years seeking contraception . Ninety-four women entered the LNG IUS group and 99 entered the OC group .  Continuation rates , reasons leading to discontinuation , adverse events , menstrual question naires , subjective well-being and sexual behavior were evaluated . Nineteen women ( 20 % ) in the LNG IUS group discontinued the study during the 1-year observation period , and 27 discontinued ( 27 % ) in the OC group . The most common reason ( 31 % ) for discontinuation in the IUS group was pain . In the OC group , hormonal side effects were the predominant medical reason for study termination . The safety and acceptability of the LNG IUS for contraception was observed to be as good as with OCs , with a high continuation rate OBJECTIVE To assess the safety and effectiveness of intrauterine device in Chinese women . METHODS In this multicenter r and omized controlled trial , a total of 24 000 women were r and omly ( 1:1:1 ) into 3 groups of Yuangong Cu 365 ( YCu365 ) , Copper T 380A ( TCu380A ) and Multiload Cu 375 ( MLCu375 ) . Clinical outcomes were assessed at 12 months post-insertion , including discontinuation due to pregnancy , expulsion , hemorrhage and downward displacement , etc . The overall and causal-specific discontinuation rates for adverse events were calculated . RESULTS At the end of the first year , the discontinuation rate of YCu365 ( 4.21 % ) was the lowest , followed by TCu380A ( 8.42 % ) and MLCu375 ( 13.91 % ) ( P < 0.01 ) . The differences of discontinuation rates for pregnancy , expulsion , hemorrhage and downward displacement between these IUDs were also significant . MLCu375 , side effect without medical treatment , fewer follow-ups , deeper uterine cavity and previous IUD failure were significantly associated with an increased risk of IUD discontinuation . CONCLUSION The newly developed indomethacin-releasing YCu365 IUD appears to perform the best . However , its long-term safety and cost-effectiveness should be further evaluated Objective : To assess whether a low-dose oral contraceptive ( OC ) is more effective than placebo treatment for dysmenorrhea pain in adolescents . Methods : This was a r and omized , double-blind , placebo-controlled clinical trial of 76 healthy adolescents aged 19 years or younger reporting moderate or severe dysmenorrhea . Subjects were r and omly allocated to receive either an OC ( ethinyl estradiol [ E2 ] 20 & mgr;g and levonorgestrel 100 & mgr;g ) or a matching placebo for 3 months . Participants used their usual pain medications as needed during the trial . The main outcome measure was score on the Moos Menstrual Distress Question naire ( pain subscale ) for the third menstrual cycle on treatment . Secondary outcomes included pain intensity ( rated 0 to 10 ) , days of any pain , days of severe pain , hours of pain on worst day , and use of pain medications . Results : The mean Moos Menstrual Distress Question naire pain score was lower ( less pain ) in the OC group than the placebo group ( 3.1 , st and ard deviation 3.2 compared with 5.8 , st and ard deviation 4.5 , P = .004 , 95 % confidence interval for the difference between means 0.88–4.53 ) . By cycle 3 , OC users rated their worst pain as less ( mean pain rating 3.7 compared with 5.4 , P = .02 ) and used fewer pain medications than placebo users ( mean pain pills used 1.3 compared with 3.7 , P = .05 ) . By cycle 3 , OC users reported fewer days of any pain , fewer days of severe pain , and fewer hours of pain on the worst pain day than placebo users ; however , these differences did not reach statistical significance . Conclusions : Among adolescents , a low-dose oral contraceptive relieved dysmenorrhea-associated pain more effectively than placebo . Level of Evidence : OBJECTIVE : To estimate whether daily educational text messages affect oral contraceptive pill ( OCP ) continuation at 6 months . METHODS : We r and omized young women electing OCPs at an urban family planning health center to either routine care or routine care plus 180 days of daily educational text messages .  Investigators masked to treatment allocation r and omized participants who were not masked to treatment . The primary outcome measure was self-reported OCP continuation through a telephone call at 6 months ( contacts between 5 and 8 months ) . RESULTS : We enrolled 962 participants ( 480 intervention and 482 routine care ) and obtained continuation data on 683 ( 346 and 337 , respectively ) . At the follow-up , 64 % of participants r and omized to the intervention were still OCP users compared with 54 % of the routine care group ( P=.005 ) . Continuation was highest in the intervention group if the interview took place while the intervention was ongoing ( 75 % compared with 54 % , P=.003 ) ; the effect of the intervention on continuation was less after the intervention ended ( 60 % compared with 54 % , P=.16 ) . Participants receiving the intervention were more likely to continue oral contraception than control participants at 6 months ( odds ratio 1.44 , 95 % confidence interval 1.03–2.00 ) in analyses adjusted for age , race or ethnicity , age at coitarche , pregnancy history , and OCP experience . CONCLUSION : The use of daily educational text messages improves OCP continuation at 6 months over routine care alone . Ten women would need to receive this simple intervention to improve continuation in one . This effect is strongest in the women whose follow-up took place while the text intervention was ongoing . CLINICAL TRIAL REGISTRATION : Clinical Trials.gov , www . Clinical Trials.gov , NCT00677703 . LEVEL OF EVIDENCE : PURPOSE To determine the effect of oral contraceptives ( OC ) on bone mass and stress fracture incidence in young female distance runners . METHODS One hundred fifty competitive female runners ages 18 - 26 yr were r and omly assigned to OC ( 30 microg of ethinyl estradiol and 0.3 mg of norgestrel ) or control ( no intervention ) for 2 yr . Bone mineral density ( BMD ) and content ( BMC ) were measured yearly by dual x-ray absorptiometry . Stress fractures were confirmed by x-ray , magnetic resonance imaging , or bone scan . RESULTS R and omization to OC was unrelated to changes in BMD or BMC in oligo/amenorrheic ( N=50 ) or eumenorrheic runners ( N=100 ) . However , treatment-received analyses ( which considered actual OC use ) showed that oligo/amenorrheic runners who used OC gained about 1 % per year in spine BMD ( P<0.005 ) and whole-body BMC ( P<0.005 ) , amounts similar to those for runners who regained periods spontaneously and significantly greater than those for runners who remained oligo/amenorrheic ( P<0.05 ) . Dietary calcium intake and weight gain independently predicted bone mass gains in oligo/amenorrheic runners . R and omization to OC was not significantly related to stress fracture incidence , but the direction of the effect was protective in both menstrual groups ( hazard ratio [ 95 % CI ] : 0.57 [ 0.18 , 1.83 ] ) , and the effect became stronger in treatment-received analyses . The trial 's statistical power was reduced by higher-than-anticipated noncompliance . CONCLUSION OC may reduce the risk for stress fractures in female runners , but our data are inconclusive . Oligo/amenorrheic athletes with low bone mass should be advised to increase dietary calcium and take steps to resume normal menses , including weight gain ; they may benefit from OC , but the evidence is inconclusive OBJECTIVE : To estimate the efficacy , cycle control , tolerability , and safety of a monophasic combined oral contraceptive containing nomegestrol acetate and 17&bgr;-estradiol ( E2 ) in comparison with drospirenone and ethinyl E2 . METHODS : In a r and omized , open-label , comparative multicenter trial , healthy women ( n=2,281 ; age 18–50 years ) at risk for pregnancy and in need of contraception were allocated in a 3:1 ratio to receive nomegestrol acetate ( 2.5 mg ) and 17&bgr;-E2 ( 1.5 mg ) in a 24–4-day regimen ( investigational drug ) or drospirenone ( 3.0 mg ) and ethinyl E2 ( 30 micrograms ) in a 21–7-day regimen ( comparator ) for 13 consecutive , 28-day cycles . The primary end point was the Pearl Index . RESULTS : The Pearl Indices for 18- to 35-year-old women in the investigational ( n=1,375 ) and comparator ( n=463 ) groups were 1.27 ( 95 % confidence interval [ CI ] 0.66–2.22 ) and 1.89 ( 95 % CI 0.69–4.11 ) , respectively . Respective 1-year cumulative pregnancy rates were 1.22 ( 95 % CI 0.69–2.16 ) and 1.82 ( 95 % CI 0.81–4.05 ) . By the end of the trial , shorter , lighter scheduled bleeding or an absence of scheduled bleeding occurred with greater frequency ( 32.9 % ) in the investigational group , whereas unscheduled bleeding or spotting episodes were low ( 16.2 % and 15.0 % in the investigational and comparator groups , respectively ) . Acne prevalence decreased from approximately 33 % at baseline to 22 % and 14 % at cycle 13 in the respective groups . In the investigational group , the most frequently reported adverse events were acne ( 16.4 % ) , weight gain ( 9.5 % ) , and irregular withdrawal bleeding ( 9.1 % ) . CONCLUSION : Nomegestrol acetate and 17&bgr;-E2 were well tolerated and provided excellent contraceptive efficacy and acceptable cycle control . CLINICAL TRIAL REGISTRATION : Clinical trials.gov , www . clinical trials.gov , NCT00413062 . LEVEL OF EVIDENCE : A prospect i ve , single-blinded , r and omized trial was initiated to determine whether injection site pain differed in adolescents receiving two concentrations of 150 mg of depot medroxyprogesterone acetate ( DMPA ) . Ninety-five adolescents seeking injectable contraception were r and omized to receive 150 mg of DMPA as follows : a deltoid injection of 1.0 mL from a single-unit-dose vial containing 150 mg/mL or 0.38 mL from a multidose vial containing 400 mg/mL of DMPA . A visual analogue scale was measured at each visit and cumulatively compared between the groups . Continuation rates were tabulated . The report of pain for the multidose vial group was significantly higher than for the unit-dose vial 
    Output:
    
The current evidence was insufficient to compare efficacy and continuation rates for hormonal and intrauterine contraceptive methods in women aged 25 years and younger