***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 
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    Input: Soft tubing Norplant(R ) contraceptive implants were studied in 1210 women for 7 years to measure the duration of effectiveness and the magnitude of the pregnancy rates over that time . Mean age at enrollment was 27.4 years . Of the enrollees , 42 % were US residents . One-sixth ( 16.1 % ) weighed > /=70 kg at the time of implant placement . At the end of 5 years , the cumulative pregnancy rate was 1.1/100 ; at the end of 7 years , it was 1.9/100 . No pregnancies occurred to any of the 400 women who enrolled in the study at age > /=30 years and who weighed < 100 kg . Among women aged 18 - 33 years , the 7-year Norplant pregnancy rates are comparable to the median pregnancy rates of tubal sterilization methods for women of the same age and duration of use . For women aged > /=34 years , without regard to weight at admission , the 7-year effectiveness of soft tubing Norplant equals or surpasses that of tubal sterilization . For continuing implant users , annual pregnancy rates < 1.0/100 in years 6 and 7 , together with low cumulative pregnancy rates , testify that Norplant capsule implants remain highly effective for 7 years A multicentre clinical trial , including 19 centres in 13 countries , assessed the contraceptive efficacy and clinical acceptability of a Silastic 382 vaginal ring releasing 20 micrograms of levonorgestrel for at least 90 days . A total of 1005 women entered the study and 8176.74 woman-months of experience was gathered . The rate of intrauterine pregnancy at one year of use was 3.6 per 100 women ( 95 % confidence interval 2.2 - 5.0 ) , and of ectopic pregnancy , 0.2 % ( one case ) . The principal reasons for discontinuation were menstrual disturbances ( 17.2 % at one year ) , vaginal symptoms ( 6.0 % ) and repeated expulsion of the ring ( 7.1 % ) . The pregnancy rate with this 20 micrograms levonorgestrel-releasing vaginal ring compares favourably with that of a low estrogen combination oral contraceptive tested by WHO and is less than half that of a progestogen-only oral contraceptive in a WHO r and omized study . It is concluded that the WHO intravaginal ring releasing an average of 20 micrograms of levonorgestrel per 24 hours is an effective method of contraception for at least one year of use OBJECTIVE To determine if increasing the hormone dose or eliminating the hormone-free interval improves key pharmacokinetic ( PK ) alterations caused by obesity during oral contraceptive ( OC )  use . STUDY DESIGN Obese [ body mass index ( BMI ) ≥30 kg/m(2 ) ] , ovulatory , otherwise healthy , women received an OC containing 20 mcg ethinyl estradiol (EE)/100 mcg levonorgestrel ( LNG ) dosed cyclically ( 21 days active pills with 7-day placebo week ) for two cycles and then were r and omized for two additional cycles to the following : continuous cycling ( CC , a dose neutral arm using the same OC with no hormone-free interval ) or increased dose ( ID , a dose escalation arm using an OC containing 30 mcg EE/150 mcg LNG cyclically ) . During Cycles 2 , 3 and 4 , outpatient visits were performed to assess maximum serum concentration ( Cmax ) , area under the curve ( AUC0-∞ ) and time to steady state as well as pharmacodynamics . These key PK parameters were calculated and compared within groups between baseline and treatment cycles . RESULTS A total of 31 women enrolled and completed the study ( CC group , n=16 ; ID group , n=15 ) . Demographics were similar between groups [ mean BMI : CC , 38 kg/m(2 ) ( S.D. 5.1 ) ; ID , 41 kg/m(2 ) ( S.D. 7.6 ) ] . At baseline , the key LNG PK parameters were no different between groups ; average time to reach steady state was 12 days in both groups ; Cmax were CC : 3.82±1.28 ng/mL and ID : 3.13±0.87 ng/mL ; and AUC0-∞ were CC : 267±115 h ng/mL and ID : 199±75 h ng/mL. Following r and omization , the CC group maintained steady-state serum levels whereas the ID group had a significantly higher Cmax ( p<.001 ) but again required 12 days to achieve steady state . However , AUC was not significantly different between CC ( 412±255 h ng/mL ) and ID ( 283±130 h ng/mL ) . Forty-five percent ( 14/31 ) of the study population had evidence of an active follicle-like structure prior to r and omization and afterwards this decreased to 9 % ( 3/31 ) . CONCLUSION Both increasing the OC dose and continuous dosing appear to counteract the impact of obesity on key OC PK parameters . IMPLICATION S Obesity adversely affects the pharmacokinetics of very low dose OC pills . Although the impact of these changes on OC efficacy is still under debate , PK parameters can be normalized in obese users by continuous dosing or increasing to a low-dose pill OBJECTIVE To examine the hypothesis that higher body weight increases the risk of oral contraceptive ( OC ) failure . METHODS We conducted a retrospective cohort analysis of data from 755 r and omly selected female enrollees of Group Health Cooperative of Puget Sound who completed an in‐person interview and dietary question naire between 1990 and 1994 as control subjects for a case‐control study of ovarian cysts . Among the 618 women who were OC ever‐users , we used Cox proportional hazards regression models to estimate the relative risk ( RR ) of pregnancy while using OCs associated with body weight quartile . RESULTS During 2822 person‐years of OC use , 106 confirmed pregnancies occurred ( 3.8 per 100 person‐years of exposure ) . After controlling for parity , women in the highest body weight quartile ( 70.5 kg or more ) had a significantly increased risk of OC failure ( RR 1.6 , 95 % confidence interval [ CI ] 1.1 , 2.4 ) compared with women of lower weight . Higher elevations of risk associated with the highest weight quartile were seen among very low‐dose OC users ( RR 4.5 , 95 % CI 1.4 , 14.4 ) and low‐dose OC users ( RR 2.6 , 95 % CI 1.2 , 5.9 ) , controlling for parity , race , religion , and menstrual cycle regularity . CONCLUSION Our findings suggest that body habitus may affect metabolism sufficiently to compromise contraceptive effectiveness . Consideration of a woman 's weight may be an important element of OC prescription Objective To measure effectiveness , adverse event experience , and acceptability of the Food and Drug Administration-approved variant of levonorgestrel capsule implants in the United States through 5 years and to examine determinants of these outcomes . Methods In a prospect i ve , multicenter study , 511 sexually active women selecting contraceptive implants  were monitored four times in the 1st year , then semiannually through 5 years . Adverse events were elicited by query and physical examination , and their incidence was measured . Lifetable analyses computed pregnancy and other discontinuation rates . Cox regression models examined effects of age , parity , and preadmission desire for more children on continuation . Removal times were analyzed by analysis of variance . Results Three pregnancies occurred , yielding a 5-year cumulative rate of 1.3 ± 0.8 per 100 users , an average annual rate of three per 1000 women , and an ectopic pregnancy rate of 0.6 per 1000 woman years . No pregnancies occurred to women weighing less than 79 kg .  Prolonged or irregular menstrual bleeding , followed distantly by headache , weight gain , and mood changes , was the most frequent medical conditions leading to removal . Weight gain averaged 1 kg per year . Each annual continuation rate was above 80 per 100 , for a cumulative 5-year rate of 39 per 100 . Continuation was age-dependent , with younger women ( younger than 25 years at entry ) having lower 5-year continuation rates than older subjects ( P < .01 ) . Tissue trauma from deeply placed or poorly aligned implants or severe reactions to local anesthetic affected subjects in 3.1 % of removals ( nine cases ) . Conclusion As measured by annual continuation rates of 80 per 100 or higher and annual pregnancy rates below one per 100 , implant contraception in the United States was found to be highly acceptable and effective , year after year , regardless of the woman 's age or family formation status . The cumulative 5-year pregnancy rate , 1.3 per 100 , is comparable to that of tubal ligation OBJECTIVE To introduce and promote the use of long-acting reversible methods of contraception ( LARC ; intrauterine contraceptives and subdermal implant ) by removing financial and knowledge barriers . STUDY DESIGN The Contraceptive CHOICE Project is a prospect i ve cohort study of 10,000 women 14 - 45 years who want to avoid pregnancy for at least 1 year and are initiating a new form of reversible contraception .  Women screened for this study are read a script regarding long-acting reversible methods of contraception to increase awareness of these options . Participants choose their contraceptive method that is provided at no cost . We report the contraceptive choice and baseline characteristics of the first 2500 women enrolled August 2007 through December 2008 . RESULTS Sixty-seven percent of women enrolled ( 95 % confidence interval , 65.3 - 69.0 ) chose  long-acting methods .  Fifty-six percent selected  intrauterine contraception  and 11 % selected the subdermal implant .  CONCLUSION Once financial barriers were removed and long-acting reversible methods of contraception were introduced to all potential participants as a first-line contraceptive option , two-thirds chose long-acting reversible methods of contraception Objective Two low-dose levonorgestrel intrauterine contraceptive systems ( LNG-IUSs ; total content 13.5 mg [ average approx . 8 μg/24 hours over the first year ; LNG-IUS 8 ] and total content 19.5 mg [ average approx . 13 μg/24 hours over the first year ; LNG-IUS 13 ] ) have previously been shown to be highly effective ( 3-year Pearl Indices : 0.33 and 0.31 , respectively ) , safe and well tolerated . The present subgroup analyses evaluated whether or not outcomes were affected by parity , age ( 18–25 vs 26–35 years ) , or body mass index ( BMI , < 30 vs ≥30 kg/m2 ) . Methods Nulliparous and parous women aged 18‒35 years with regular menstrual cycles ( 21‒35 days ) requesting contraception were r and omized to 3 years of LNG-IUS 8 or LNG-IUS 13 use . Results In the LNG-IUS 8 and LNG-IUS 13 groups , 1432 and 1452 women , respectively , had a placement attempted and were included in the full analysis set ; 39.2 % , 39.2 % and 17.1 % were 18–25 years old , nulliparous and had a BMI ≥30 kg/m2 , respectively . Both systems were similarly effective regardless of age , parity or BMI ; the subgroup Pearl Indices had widely overlapping 95 % confidence intervals .  Placement of LNG-IUS 8 and LNG-IUS 13 was easier ( p < 0.0001 ) and less painful ( p < 0.0001 ) in women who had delivered vaginally than in women who had not . The complete/partial expulsion rate was 2.2–4.2 % across all age and parity subgroups and higher in parous than in nulliparous women ( p = 0.004 ) . The incidence of pelvic inflammatory disease was 0.1–0.6 % across all age and parity subgroups : nulliparous and younger women were not at higher risk than parous and older women , respectively . The ectopic pregnancy rate was 0.3–0.4 % across all age and parity subgroups . Across all age and parity subgroups , the 3-year completion rate was 50.9–61.3 % for LNG-IUS 8 and 57.9–61.1 % for LNG-IUS 13 , and was higher ( p = 0.0001 ) among older than younger women in the LNG-IUS 8 group only . Conclusions LNG-IUS 8 and LNG-IUS 13 were highly effective , safe and well tolerated regardless of age or parity . Trial Registration Clinical trials.gov A 5-year trial of a two-rod contraceptive implant , which releases the progestin levonorgestrel ( LNG rod ) , was conducted at four clinics with 594 women . Mean age and weight at admission were 25.5 years and 62.4 kg , respectively . Consent to continue 
    Output:
    
AUTHORS ' CONCLUSIONS The evidence generally did not indicate an association between higher BMI or weight and effectiveness of hormonal contraceptives .
Studies using BMI , rather than weight alone , can provide information about whether body composition is related to contraceptive effectiveness .
The contraceptive methods examined here are among the most effective when used according to the recommended regimen .