***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: OBJECTIVE The aim of this study was to compare perinatal outcomes of patients with second-trimester ultrasonographic evidence of preterm dilatation of the internal os treated with cerclage  versus those of patients not treated with cerclage .  STUDY DESIGN From May 1998 through June 1999 patients with ultrasonographic evidence of preterm dilatation of the internal os between 16 and 24 weeks ' gestation were r and omly assigned to receive a McDonald cerclage or no cerclage .  Before r and om assignment all patients underwent amniocentesis and urogenital cultures and then received 48 hours of therapy with indomethacin and antibiotics . After treatment each patient was followed up as an outpatient with bed rest and weekly ultrasonographic evaluation . RESULTS Of the 61 patients 31 were r and omly assigned to cerclage and 30 were r and omly assigned to no cerclage . There were no differences between groups with respect to maternal demographic characteristics , risk factors for preterm birth , cervical measurements , rescue procedures , readmission , chorioamnionitis , and abruptio placentae . The mean gestational age at delivery ( 33.5 + /- 6.3 weeks ) and the perinatal death rate ( 12 . 9 % ) in the cerclage group were similar to the mean gestational age at delivery ( 34.7 + /- 4.7 weeks ; P = .4 ) and the perinatal death rate ( 10.0 % ; P = .9 ) in the no-cerclage group . CONCLUSION Treatment with McDonald cerclage of preterm dilatation of the cervix detected ultrasonographically during the second trimester did not improve perinatal outcomes 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 To compare cervical length measurements obtained at 11 to 14 weeks and 22 to 24 weeks of gestation in an unselected group of pregnant women and to correlate the measurements with time of delivery . METHODS This was a prospect i ve study involving 529 pregnant women attending for routine antenatal care who underwent transvaginal scans at 11 - 14 weeks and 22 - 24 weeks for evaluation of cervical length .  The mean cervical length was calculated at both stages of gestation and lengths were compared between groups which delivered at term or prematurely , this being defined as delivery before 37 completed weeks of gestation . RESULTS The mean cervical lengths at 11 - 14 and 22 - 24 weeks were , respectively , 42.4 mm and 38.6 mm . Cervical length at 11 - 14 weeks was not significantly different between the groups which delivered at term ( 42.7 mm ) and preterm ( 40.6 mm ) . However , at the 22 - 24-week evaluation , cervical length was significantly shorter in the group which had a preterm delivery than in that which had a term delivery ( 26.7 mm and 39.3 mm , respectively ; P = 0.0001 ) . In the group of women with a previous history of one or more preterm deliveries , there was a greater shortening in cervical length from the first to the second evaluation than there was in the group of women with no previous history of preterm delivery . This shortening was also more pronounced in the group which delivered prematurely ( from 40.6 mm to 26.7 mm ) than in that which delivered at term ( from 42.7 mm to 39.3 mm ) . CONCLUSION There is a spontaneous shortening in the pregnant cervix from the first to the second trimester of pregnancy . The shortening is more rapid in pregnant women who deliver prematurely and who have a history of previous preterm delivery BACKGROUND Measurement of mid-gestation cervix length has become a common screening tool for preterm birth . Our study was design ed to assess the value of cervix length and serum relaxin in the prediction of spontaneous preterm birth at < 35 and < 37 weeks ' gestation in a general obstetric population . METHODS A prospect i ve cohort of women with a singleton pregnancy had blood collected at 24 and 28 weeks ' gestation for determination of serum relaxin immediately before transvaginal ultrasound measurement of cervical length . Patients and referring physicians were blinded to cervix length and relaxin levels to preclude changes in management . The primary outcomes were spontaneous delivery at < 35 and < 37 weeks ' gestation . RESULTS A total of 1004 women entered the study . Delivery data were not available for 20 women who delivered elsewhere . Twenty women were excluded because preterm delivery was undertaken because of pregnancy abnormalities . Of the 964 women with known gestational age at delivery , 46 ( 4.8 % ) delivered at < 37 weeks and 16 ( 1.7 % ) at < 35 weeks ' gestation . Mean cervix length at 28 weeks ( 36.7 + /- 7.3 mm ) was significantly shorter than at 24 weeks ( 37.8 + /- 7.1 mm ) ( P < 0.001 ) . Cervix length at 24 and 28 weeks ' gestation was equally predictive of preterm birth . A cervix length of < or = 30 mm at 28 weeks had a sensitivity of 57.1 % , a specificity of 81.8 % , and a positive predictive value of 4.5 % for birth at < 35 weeks . Serum relaxin levels were not correlated with cervix length at either 24 or 28 weeks . Serum relaxin at 24 and 28 weeks ' gestation was not associated with preterm birth before or after controlling for patient characteristics and cervix length . CONCLUSION Serum relaxin levels at 24 and 28 weeks ' gestation are not associated with preterm birth . Although cervix length is associated with preterm birth , its positive predictive value is low . Given the lack of proven therapies for those at risk , cervix length does not appear to be a useful screening tool for preterm delivery in the general obstetric population OBJECTIVE To investigate the efficacy of vaginal progesterone to prevent early preterm birth in women with sonographic evidence of a short cervical length in the midtrimester . METHODS This was a planned , but modified , secondary analysis of our multinational , multicenter , r and omized , placebo-controlled trial , in which women were r and omized between 18 + 0 and 22 + 6 weeks of gestation to receive daily treatment with 90 mg of vaginal progesterone gel or placebo .  Cervical length was measured with transvaginal ultrasound at enrollment and at 28 weeks of gestation . Treatment continued until either delivery , 37 weeks of gestation or development of preterm rupture of membranes . Maternal and neonatal outcomes were evaluated for the subset of all r and omized women with cervical length < 28 mm at enrollment . The primary outcome was preterm birth at < /= 32 weeks . RESULTS A cervical length < 28 mm was identified in 46 r and omized women : 19 of 313 who received progesterone and 27 of 307 who received the placebo .  Baseline characteristics of the two groups were similar . In women with a cervical length < 28 mm , the rate of preterm birth at < /= 32 weeks was significantly lower for those receiving progesterone than it was for those receiving the placebo ( 0 % vs. 29.6 % , P = 0.014 ) . With progesterone , there were fewer admissions into the neonatal intensive care unit ( NICU ; 15.8 % vs. 51.9 % , P = 0.016 ) and shorter NICU stays ( 1.1 vs. 16.5 days , P = 0.013 ) . There was also a trend toward a decreased rate of neonatal respiratory distress syndrome ( 5.3 % vs. 29.6 % , P = 0.060 ) . CONCLUSION Vaginal progesterone may reduce the rate of early preterm birth and improve neonatal outcome in women with a short sonographic cervical length OBJECTIVES To assess the role of cervical sonography and to compare various sonographic cervical parameters in their ability to predict spontaneous preterm birth in high-risk singleton gestations . DESIGN A prospect i ve cohort of 469 high-risk gestations were longitudinally evaluated between 15 and 24 weeks ' gestation on 1265 occasions with transvaginal cervical sonography and transfundal pressure .  The cervical parameters obtained were funnel width and length , cervical length , percent funneling and cervical index . The information obtained was used for patient management . Restriction of physical activities was initiated at cervical lengths of < or = 2.5 cm with cerclage as an option for cervical lengths of < or = 2.0 cm . RESULTS Receiver operating characteristic curve analyses showed that a cervical length of < or = 2.5 cm between 15 and 24 weeks ' gestation was equal to the other sonographic cervical parameters in its ability to predict spontaneous preterm birth . The sensitivities for delivery at < 28 , < 30 , < 32 and < 34 weeks ' gestation were 94 % , 91 % , 83 % and 76 % , respectively , while the negative predictive values were 99 % , 99 % , 98 % and 96 % , respectively . The placement of a cerclage did not influence the positive and negative predictive values . In comparison to women with other risk factors , cervical length was best in the prediction of preterm birth in women with a prior mid-trimester loss ; an optimal cut-off of < or = 1.5 cm had sensitivities for delivery at < 28 , < 30 , < 32 and < 34 weeks ' gestation of 100 % , 100 % 92 % and 81 % , respectively . The rate of preterm delivery at < 34 weeks ' gestation increased dramatically when the cervical length was < or = 1.5 cm . Cervical length was the only independent variable that entered the logistic regression model for the prediction of preterm delivery at < 34 weeks ' gestation . CONCLUSIONS In high-risk singleton gestations a cervical length of < or = 2.5 cm was equal to other sonographic cervical parameters in its ability to predict spontaneous preterm birth and was better for the prediction of earlier forms of prematurity ( at < 28 and < 30 weeks ) than later forms ( at < 32 and < 34 weeks ) . The optimal cervical lengths and their performance for predicting prematurity may be influenced by obstetric risk factors In a cohort of 43 women with viable , singleton pregnancies , cervical dilatation greater than 4 cm , and absent labor between 20 and 27 weeks gestation , 22 women who underwent emergency cerclage within six hours of admission , were compared prospect ively with 15 women who elected conservative bed rest treatment .  The two groups were demographically similar . Emergency cervical cerclage result ed in a longer mean gestational age at delivery compared to bed rest ( p = 0.001 ) . Women treated with cerclage required a significantly shorter period of antepartum hospitalization ( p = 0.001 ) , required less tocolysis ( p = 0.005 ) , and experienced fewer preterm membrane ruptures compared to women in the bed rest group ( p = 0.01 ) , although the latency period , following preterm rupture of membranes was shorter in the cerclage group ( p = 0.005 ) . There was no statistical difference in the frequencies of chorioamnionitis , maternal morbidity and cesarean section between the two groups . Although the perinatal mortality in the two groups was not significantly different ( p = 0.3 ) , emergency cerclage result ed in a significantly higher mean birth weight compared to conservative bed rest treatment ( p 
    Output:
    
Use of the ultrasonographic technique review ed in this guideline may help identify women at risk of preterm birth and , in some circumstances , lead to interventions that may reduce the rate of preterm birth .