***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: Internal os cerclage for cervical incompetence was performed in 90 patients who had previous McDonald procedure failure ( 70 patients ) or had unfavorable cervical anatomy ( short or lacerated cervix ) for primary McDonald type cerclage ( 20 patients ) . Two different techniques were used : the Shirodkar operation ( n = 44 ) with Mersilene b and , and a simpler new technique ( n = 46 ) . The new technique is characterized by anterior colpotomy for exposure of the internal os , and a 0.6 mm nylon suture encircling the cervix to be tied high in the posterior fornix . The pregnancy outcome for both groups was similar . Late abortions of 8.7 and 11 % and premature deliveries of 13 and 18 % occurred in the new technique and the Shirodkar groups , respectively . The removal of the suture was generally difficult in the Shirodkar group and in eight patients analgesia and sedation were required . In the new technique group , the removal was easier and in only one patient was sedation required ( p less than 0.0001 ) . Severe vaginal discharge was found in 52 % of the Shirodkar patients and none in the other group . Apparently the monofilament nylon suture prevented this side effect . It seems that the new technique is simpler to perform , involves fewer side effects , the removal of the suture is easier , and it is as effective as the Shirodkar procedure OBJECTIVE Our purpose was to determine the association between the presence of bacterial vaginosis , fetal fibronectin , and a short cervix and the risk of  spontaneous preterm birth of twins . STUDY DESIGN We prospect ively screened 147 women with twins at 24 and 28 weeks ' gestation for more than 50 potential risk factors for spontaneous preterm birth .  We also measured  cervical length with ultrasound scans and tested for the presence of bacterial vaginosis . Fetal fibronectin level was evaluated every 2 weeks from 24 to 30 weeks ' gestation . Outcomes included spontaneous preterm birth at < 32 weeks , < 35 weeks , and < 37 weeks . RESULTS Among twin as compared with singleton pregnancies , a cervical length < or = 25 mm was more common at both 24 and 28 weeks , a statistically significant difference . There were no significant differences in most other risk factors . Of the factors evaluated by means of univariate analysis at 24 weeks , only a short cervix ( < or = 25 mm ) was consistently associated with spontaneous preterm birth . The odds ratio and 95 % confidence interval for spontaneous preterm birth at < 32 weeks , < 35 weeks , and < 37 weeks were 6.9 ( 2.0 to 24.2 ) , 3.2 ( 1.3 to 7.9 ) , and 2.8 ( 1.1 to 7.7 ) . At 28 weeks , a cervical length < or = 25 mm was not a strong predictor of spontaneous preterm birth . At both 28 weeks ( odds ratio , 9.4 ; confidence interval , 1.0 to 67.7 ) and 30 weeks ( odds ratio 46.1 ; confidence interval , 4.2 to 1381 ) , a positive fetal fibronectin result was significantly associated with spontaneous preterm birth at < 32 weeks . Bacterial vaginosis at 24 or 28 weeks was not associated with spontaneous preterm birth of twins . Multivariate analysis confirmed the association between cervical length < or = 25 mm at the 24-week visit and spontaneous preterm birth and also confirmed that at 24 weeks the other risk factors were less consistently and often not statistically significantly associated with spontaneous preterm birth . Of the risk factors evaluated at 28 weeks , only a positive fetal fibronectin was associated with a significantly increased risk for spontaneous preterm birth . CONCLUSIONS Most known risk factors for spontaneous preterm birth were not significantly associated with  spontaneous preterm birth of twins . At 24 weeks , cervical length < or = 25 mm was the best predictor of spontaneous preterm birth at < 32 weeks , < 35 weeks , and < 37 weeks . Of the risk factors evaluated at 28 weeks , fetal fibronectin was the only statistically significant predictor of spontaneous preterm birth at < 32 weeks OBJECTIVE We sought to provide evidence -based guidelines for using progestogens for the prevention of preterm birth ( PTB ) .  METHODS Relevant documents , in particular r and omized trials , were identified using PubMed ( US National Library of Medicine , 1983 through February 2012 ) publications , written in English , which evaluate the effectiveness of progestogens for prevention of PTB . Progestogens evaluated were , in particular , vaginal progesterone and 17-alpha-hydroxy-progesterone caproate . Additionally , the Cochrane Library , organizational guidelines , and studies identified through review of the above were utilized to identify relevant articles . Data were evaluated according to population studied , with separate analyses for singleton vs multiple gestations , prior PTB , or short transvaginal ultrasound cervical length ( CL )  , and combinations of these factors . Consistent with US Preventive Task Force suggestions , references were evaluated for quality based on the highest level of evidence , and recommendations were grade d. RESULTS AND RECOMMENDATIONS Summary of r and omized studies indicates that in women with singleton gestations , no prior PTB , and short CL ≤ 20 mm at ≤ 24 weeks , vaginal progesterone , either 90-mg gel or 200-mg suppository , is associated with reduction in PTB and perinatal morbidity and mortality , and can be offered in these cases . The issue of universal CL screening of singleton gestations without prior PTB for the prevention of PTB remains an object of debate . CL screening in singleton gestations without prior PTB can not yet be universally m and ated . Nonetheless , implementation of such a screening strategy can be viewed as reasonable , and can be considered by individual practitioners , following strict guidelines . In singleton gestations with prior PTB 20 - 36 6/7 weeks , 17-alpha-hydroxy-progesterone caproate 250 mg intramuscularly weekly , preferably starting at 16 - 20 weeks until 36 weeks , is recommended . In these women with prior PTB , if the transvaginal ultrasound CL shortens to < 25 mm at < 24 weeks , cervical cerclage may be offered . Progestogens have not been associated with prevention of PTB in women who have in the current pregnancy multiple gestations , preterm labor , or preterm premature rupture of membranes . There is insufficient evidence to recommend the use of progestogens in women with any of these risk factors , with or without a short CL OBJECTIVE To compare preterm delivery rates ( before 34 weeks of gestation ) and neonatal morbidity and mortality in patients with risk factors or symptoms of cervical incompetence managed with therapeutic McDonald cerclage and bed rest versus bed rest alone .  STUDY DESIGN Cervical length was measured in patients with risk factors or symptoms of cervical incompetence . Risk factors for cervical incompetence included previous preterm delivery before 34 weeks of gestation that met clinical criteria for the diagnosis of cervical incompetence , previous preterm premature rupture of membranes before 32 weeks of gestation , history of cold knife conization , diethylstilbestrol exposure , and uterine anomaly . When a cervical length of < 25 mm was measured before a gestational age of 27 weeks , a r and omization for therapeutic cerclage and bed rest ( cerclage group ) or bed rest alone ( bed rest group ) was performed . The analysis is based on intention to treat . RESULTS Of the 35 women who met the inclusion criteria , 19 were allocated r and omly to the cerclage group and 16 to the bed rest group . Both groups were comparable for mean cervical length and mean gestational age at time of r and omization , mean overall 20 mm and 21 weeks . Preterm delivery before 34 weeks was significantly more frequent in the bed rest group than in the cerclage group ( 7 of 16 vs none , respectively ; P = .002 ) . There was no statistically significant difference in neonatal survival between the groups ( 13 neonates survived in the bed rest group vs all in the cerclage group ) . The compound neonatal morbidity , defined as admission to the neonatal intensive care unit or neonatal death , was significantly higher in the bed rest group than in the cerclage group ( 8 of 16 vs 1 of 19 , respectively ; P = .005 ; RR = 9.5 , 95 % CI , 1.3 - 68.1 ) . CONCLUSIONS Therapeutic cerclage with bed rest reduces preterm delivery before 34 weeks of gestation and compound neonatal morbidity in women with risk factors and /or symptoms of cervical incompetence and a cervical length of < 25 mm before 27 weeks of gestation OBJECTIVE The purpose of this study was to determine the efficacy of cerclage and bed rest versus bed rest-only for the prevention of preterm birth in women with a short cervix found on transvaginal ultrasound examination . STUDY DESIGN Women with > or = 1 of high-risk factors for preterm birth ( > or = 1 preterm birth at < 35 weeks of gestation , > or = 2 curettages , diethylstilbestrol exposure , cone biopsy , Mullerian anomaly , or twin gestation ) were screened with  transvaginal ultrasonography of the cervix every 2 weeks from 14 weeks of gestation to 23 weeks 6 days of gestation . Enrollment was offered to both asymptomatic women who were at high risk and who were identified to have short cervix ( < 25 mm ) or significant funneling ( > 25 % ) and nonscreened women who were at low risk and who were identified incidentally . The women who gave written consent were assigned r and omly to receive either McDonald cerclage or bed rest-only . Both groups received similar counseling and treatment . Primary outcome was preterm birth at < 35 weeks of gestation . RESULTS Sixty-one women were assigned r and omly . Forty-seven pregnancies ( 77 % ) were high-risk singleton gestations . Thirty-one women ( 51 % ) were allocated to cerclage , and 30 women ( 49 % ) were allocated to bed rest . There were no differences between the groups in demographic characteristics , risk factors , and cervical variables . Preterm birth at < 35 weeks of gestation occurred in 14 women ( 45 % ) in the cerclage group and in 14 women ( 47 % ) in the bed rest group ( relative risk , 0.94 ; 95 % CI , 0.34 - 2.58 ) . There was no difference in any obstetric or neonatal outcomes . A sub analysis of singleton pregnancies with previous preterm birth at < 35 weeks of gestation and a short cervix of < 25 mm ( n = 31 women ) also revealed no significant difference in recurrent preterm birth at < 35 weeks of gestation ( 40 % vs 56 % ; relative risk , 0.52 ; 95 % CI , 0.12 - 2.17 ) . CONCLUSION Cerclage did not prevent preterm birth in women with a short cervix . These results should be confirmed by larger trials To determine the value of transvaginal sonography in women with a previous history of second trimester miscarriage due to cervical incompetence , 55 patients were subjected to either elective cervical cerclage or follow-up  ( every second patient ) with weekly evaluations of the cervix by transvaginal ultrasonography . Emergency cerclage was applied when significant cervical changes were noted . All patients were evaluated with cervical cultures and ultrasound .  Women with infection , fibroids , uterine malformations and multiple pregnancies were excluded from the study . The study population was divided in two groups . In group I ( n=27 ) elective cerclage was applied during the 14th week . Women in group II ( n=28 ) were subjected to serial weekly evaluations of the cervix by transvaginal ultrasonograms . In 18 cases emergency cerclage was applied due to significant cervical changes . In group I , labor started before the 33rd week in two cases ( 7.4 % ) , between 33 and 37 weeks in nine ( 33.3 % ) and after the 37th week in 16 cases ( 59.2 % ) . Out of the 18 patients in group II who had cervical cerclage after ultrasonographic evaluation , four ( 22.2 % ) delivered before the 33rd week , three ( 16.6 % ) between 33 and 37 weeks and 11 ( 61.1 % ) after the 37th week . No statistical difference was noted between the two groups referring to pregnancy outcome ( p<0.1 ) . We concluded that ultrasound-guided management despite cervical shortening , does not result in unfavorable pregnancy outcome . A significant number of patients can avoid the operation OBJECTIVE Our purpose was to determine the impact of cerclage placement on obstetric outcome in twin gestations with a shortened cervical length . STUDY DESIGN A prospect i ve cohort study of 147 consecutive twin pregnancies ( July 1994 to March 2001 ) who underwent transvaginal ultrasonographic cervical length measurement between 18 and 26 weeks ' gestation .  Cerclage was offered to women with cervical lengths < or = 25 mm . Patients were segregated into quartiles by cervical length . Regression analysis and chi(2 ) tests were used to 
    Output:
    
Based on these Level 1 data , cerclage can not currently be recommended for clinical use in twin pregnancies with a maternal short cervical length in the second trimester .