***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: OBJECTIVES To establish the relationship of cervical length at 23 weeks of gestation to the risk of  spontaneous delivery before 33 weeks and to determine the possible additional risk if funneling is present . METHODS During a 36-month period , 6819 women with singleton pregnancies underwent transvaginal sonographic cervical assessment at 22 - 24 weeks as a screening test for preterm delivery . The distribution of cervical length and the prevalence of funneling , defined as dilatation of the internal os of > or = 5 mm in width , were established . Women who underwent cervical cerclage , iatrogenic preterm delivery or were lost to follow-up were excluded from further analysis . In the remaining 6334 pregnancies , logistic regression was used to examine the contribution of  cervical length and funneling to the risk of spontaneous preterm delivery before 33 weeks . RESULTS The median cervical length was 36 mm and in 1.6 % of cases the length was < or = 15 mm . There was a significant inverse association between cervical length and percentage rate of spontaneous delivery before 33 weeks . Funneling of the internal os was present in about 4 % of pregnancies and the prevalence decreased with increasing cervical length from 98 % when the length was < or = 15 mm to about 25 % for lengths of 16 - 30 mm and less than 1 % at lengths of > 30 mm . The rate of preterm delivery was 6.9 % in those with funneling compared to 0.7 % in those without funneling ( chi2 = 86.7 ; P < 0.0001 ) . However , logistic regression analysis demonstrated that funneling did not provide a significant additional contribution to cervical length in the prediction of spontaneous delivery before 33 weeks ( odds ratio for short cervix = 24.9 , Z = 4.43 , P < 0.0001 ; odds ratio for funneling = 1.8 , Z = 0.84 , P = 0.40 ) . CONCLUSION In the prediction of preterm delivery , funneling does not provide any significant contribution in addition to cervical length OBJECTIVE This study was undertaken to evaluate the efficacy of maintenance oral nifedipine in patients initially treated with intravenous magnesium sulfate for preterm labor . STUDY DESIGN Patients with a diagnosis of preterm labor between 24 and 33.9 weeks ' gestation were r and omly assigned to receive either maintenance tocolytic therapy with oral nifedipine ( 20 mg every 4 - 6 hours ) or no treatment ( control ) after discontinuation of magnesium tocolysis .  Pregnancy and neonatal outcomes were evaluated . A sample size of 50 patients was required to detect a 10-day difference in mean time gained ( beta = .2 , alpha = .05 ) . Statistical analyses were based on intent to treat . The t , chi(2 ) , and Fisher exact tests were performed . RESULTS Seventy-four patients were r and omly assigned to receive either oral nifedipine ( n = 37 ) or no treatment ( n = 37 ) . There were no statistically significant differences in age , race , parity , preterm delivery risk factors , enrollment gestational age , results of cervical examination , delivery gestational age , time gained , or neonatal complications between the groups . Delivery gestational age ( mean + /- SD ) was 35.4 + /- 3.2 weeks for patients r and omly assigned to receive nifedipine and 35.3 + /- 3.2 weeks for patients who received no treatment ( P = .9 ) . Time gained during pregnancy was 37 + /- 23.9 days in the nifedipine group and 32.8 + /- 20.4 days in the control group ( P = .4 ) . CONCLUSION Maintenance therapy with oral nifedipine does not significantly prolong pregnancy in patients initially treated with intravenous magnesium sulfate for preterm labor OBJECTIVES To determine whether progesterone supplementation alters cervical shortening in women at increased risk for preterm birth . METHODS We performed a planned secondary analysis from a large , multinational preterm birth prevention trial of daily intravaginal progesterone gel , 90 mg , compared with placebo in women with a history of spontaneous preterm birth or premature cervical shortening .  Transvaginal cervical length measurements were obtained in all r and omized patients at baseline ( 18 + 0 to 22 + 6 weeks ' gestation ) and at 28 weeks ' gestation . For this secondary analysis , the difference in cervical length between these time points was compared for the study population with a history of spontaneous preterm birth and for a population with premature cervical shortening ( < or = 30 mm ) at r and omization . Differences between groups in cervical length for the 28-week examination were analyzed using ANCOVA , including adjustment for relevant clinical parameters and maternal characteristics . RESULTS Data were analyzed from 547 r and omized patients with a history of preterm birth . The progesterone-treated patients had significantly less cervical shortening than the placebo group ( difference 1.6 ( 95 % CI , 0.3 - 3.0 ) mm ; P = 0.02 , ANCOVA ) . In the population of 104 subjects with premature cervical shortening at r and omization , the cervical length also differed significantly on multivariable analysis , with the treatment group preserving more cervical length than the placebo group ( difference 3.3 ( 95 % CI , 0.3 - 6.2 ) mm ; P = 0.03 , ANCOVA ) , with adjustment for differences in cervical length at screening . A significant difference was also observed between groups for categorical outcomes including the frequency of cervical length progression to < or = 25 mm and a > or = 50 % reduction in cervical length from baseline in this sub population . CONCLUSIONS Intravaginal progesterone enhances preservation of cervical length in women at high risk for preterm birth OBJECTIVE Our purpose was to compare the accuracy of ultrasonographic and manual cervical examinations for the prediction of preterm delivery . STUDY DESIGN One hundred two singleton pregnancies at high risk for preterm delivery were followed up prospect ively from 14 to 30 weeks with both serial cervical ultrasonography measurements and manual examinations of the length of the cervix . The primary outcome studied was preterm ( < 35 weeks ) delivery . RESULTS Excluding six induced preterm deliveries , 96 pregnancies were analyzed . The mean cervical length measured by ultrasonography was 20.6 mm in pregnancies delivered preterm ( n = 17 ) and 31.3 mm in pregnancies delivered at term ( n = 79 ) ( p = 0.003 ) ; the mean cervical lengths measured by manual examination were 16.1 mm and 18.6 mm in the same preterm and term pregnancies , respectively ( not significant ) . The sixteenth- and twentieth-week ultrasonographic cervical lengths predicted preterm delivery most accurately ( p < 0.0005 ) . The 25th percentiles of ultrasonographic ( 25 mm ) and manual ( 16 mm ) cervical lengths showed relative risks for preterm delivery of 4.8 ( 95 % confidence interval 2.1 to 11.1 , p = 0.0004 ) and 2.0 ( 95 % confidence interval 0.5 to 4.7 , p = 0.1 ) , respectively ; sensitivity , specificity , and positive and negative predictive values were 59 % , 85 % , 45 % , 91 % , and 41 % , 77 % , 28 % , and 86 % , respectively . CONCLUSION Cervical length measured by ultrasonography is a better predictor of preterm delivery than is cervical length measured by manual examination . Cervical ultrasonography in patients at high risk for preterm birth seems to be most predictive of preterm delivery when it is performed between 14 and 22 weeks ' gestation OBJECTIVE The objective of the study was to determine whether myometrial electrical activity can differentiate false from true preterm labor . STUDY DESIGN Electrical uterine myography ( EUM ) was measured prospect ively on 87 women , gestational age less than 35 weeks . The period between contractions , power of contraction peaks and movement of center of electrical activity ( RMS ) , was used to develop an index score ( 1 - 5 ) for prediction of preterm delivery ( PTD ) within 14 days of the test . The score was compared with  fetal fibronectin ( fFN ) and cervical length ( CL ) . RESULTS Patients delivering within 14 days from testing showed a higher index and mean RMS ( P = .000 ) . No patients with EUM index scores of 1 - 2 delivered in this time frame . Combining EUM with CL or fFN increased predictability . Logistic regression revealed that history of PTD and EUM index had 4- to 5-fold increased risk for PTD . Gestational age at testing , body mass index , fFN , and CL were nonsignificant contributors to PTD risk . CONCLUSION Measuring myometrial electrical activity may enhance identification of patients in true premature labor OBJECTIVE To compare the effects of therapeutic cerclage and bed rest vs. just bed rest on cervical length and to relate these effects to the risk of preterm delivery . DESIGN Cervical length was measured in patients at high risk of cervical incompetence . When a cervical length < 25 mm was measured before 27 weeks ' gestation , r and omization for therapeutic cerclage and bed rest vs. just bed rest was performed . After r and omization , cervical length was measured weekly . For statistical analysis , t-test and Fisher 's exact tests were used and P < 0.05 was considered statistically significant . RESULTS Nineteen women were r and omly allocated to receive a therapeutic cerclage and bed rest  and 16 were allocated to receive bed rest only .  Mean cervical lengths and mean gestational ages before r and omization were comparable between both groups , overall 19.8 mm and 20.7 weeks . Cervical length was measured again at a mean gestation of 22.1 weeks . Mean cervical length ( 31 mm ) was significantly ( P < 0.0001 ) longer after cerclage than after bed rest only ( 19 mm ) . A cervical length > or = 25 mm was measured in 22 of the 35 included women , 16 in the cerclage group and six in the bed-rest group ( P = 0.006 ) . Of these 22 women , only one delivered before 34 weeks ' gestation , which was significantly less frequent than six out of 13 women with a cervical length < 25 mm ( P = 0.006 ) . CONCLUSIONS Therapeutic cerclage with bed rest increases cervical length more often than bed rest alone . A postintervention cervical length > or = 25 mm reduces the risk of preterm delivery in women at high risk of cervical incompetence and a preintervention cervical length < 25 mm BACKGROUND The measurement of the frequency of uterine contractions has not been useful for reducing the rate of preterm delivery in r and omized trials . Nonetheless , ambulatory monitoring of contractions continues to be used in clinical practice . METHODS We assessed the frequency of uterine contractions as a predictor of the risk of  spontaneous preterm delivery before 35 weeks of gestation . We enrolled women with singleton pregnancies between 22 and 24 weeks of gestation . The women used a contraction monitor at home to record contraction frequency twice daily on 2 or more days per week from enrollment to delivery or 37 weeks of gestation . RESULTS We obtained 34,908 hours of successful monitoring recordings from 306 women . Although more contractions were recorded from women who delivered before 35 weeks than from women who delivered at 35 weeks or later , we could identify no threshold frequency that effectively identified women who delivered preterm infants . The sensitivity and positive predictive value of a maximal hourly frequency of contractions of four or more between 4 p.m. and 3:59 a.m. were 9 percent and 25 percent , respectively , at 22 to 24 weeks and 28 percent and 23 percent at 27 to 28 weeks . Other proposed screening tests , such as digital and ultrasound evaluations of the cervix and assays for fetal fibronectin in cervicovaginal secretions , also had low sensitivity and positive predictive value for preterm labor . CONCLUSIONS Although the likelihood of preterm delivery increases with an increased frequency of uterine contractions , measurement of this frequency is not clinical ly useful for predicting preterm delivery Background Indirect comparisons are becoming increasingly popular for evaluating medical treatments that have not been compared head-to-head in r and omized clinical trials ( RCTs ) . While indirect methods have grown in popularity and acceptance , little is known about the fragility of confidence interval estimations and hypothesis testing relying on this method . Methods We present the findings of a simulation study that examined the fragility of indirect confidence interval estimation and hypothesis testing relying on the adjusted indirect method . Findings Our results suggest that , for the setting s considered in this study , indirect confidence interval estimation suffers from under-coverage while indirect hypothesis testing suffers from low power in the presence of moderate to large between- study heterogeneity . In addition , the risk of overestimation is large when the indirect comparison of interest relies on just one trial for one of the two direct comparisons . Interpretation Indirect comparisons typically suffer from low power . The risk of imprecision is increased when comparisons are unbalanced OBJECTIVE To assess whether cervical cerclage in women deemed to be at increased risk of cervical incompetence prolongs pregnancy and thereby improves fetal and neonatal 
    Output:
    
Both interventions were associated with a statistically significant reduction in the risk of preterm birth at < 32 weeks of gestation and composite perinatal morbidity and mortality compared with placebo/no cerclage .
Adjusted indirect metaanalyses did not show statistically significant differences between vaginal progesterone and cerclage in the reduction of preterm birth or adverse perinatal outcomes .
CONCLUSION Based on state-of-the-art methods for indirect comparisons , either vaginal progesterone or cerclage are equally efficacious in the prevention of  preterm birth in women with a sonographic short cervix in the mid trimester , singleton gestation , and previous preterm birth .