Prediction of preterm delivery in twins by cervical assessment at 23 weeks.

OBJECTIVE: To establish the relation between cervical length at 23 weeks of gestation in twin pregnancies and risk of spontaneous delivery before 33 weeks. METHODS: Cervical length was measured by transvaginal sonography at 23 (range 22-24) weeks of gestation in 464 twin pregnancies attending for routine antenatal care. In the patients who were managed expectantly the relation between cervical length and the rate of spontaneous delivery before 33 weeks was determined. RESULTS: The cervical length distribution was skewed to the left and the median value was 36 mm. The rate of spontaneous delivery before 33 weeks was inversely related to cervical length at 23 weeks. It increased gradually from about 2.5% at 60 mm, to 5% at 40 mm and 12% at 25 mm, and exponentially below this length to 17% at 20 mm and 80% at 8 mm. Cervical length of 20 mm or less is found in about 8% of the population and this group contained about 40% of women delivering spontaneously before 33 weeks. CONCLUSIONS: In twin pregnancies measurement of cervical length provides useful prediction of risk for spontaneous early preterm delivery.     

Cervical length, multifetal pregnancy reduction, and prediction of preterm birth

PURPOSE: To evaluate the application of transvaginal sonography assessment of cervical length before fetal reduction for predicting spontaneous preterm birth in triplet gestations reduced to twins. METHODS: This retrospective study was conducted at the ultrasound unit of a university-affiliated municipal hospital. The study cohort consisted of 25 women with triplet gestations following ovulation induction or assisted-reproduction techniques who underwent fetal reduction to twins. Cervical length was assessed via transvaginal sonography before fetal reduction, and data on pregnancy outcome were retrieved from maternal records and/or maternal interviews. RESULTS: Cervical length (mean +/- SD) at reduction was 4.0 +/- 0.85 (range: 1.2-5.5). Five women were excluded from statistical evaluation because pregnancy complications precluded spontaneous delivery. Two of 3 (67%) women with a cervical length of <3.5 cm delivered prior to 33 weeks' gestation compared with 1/17 (6%) women with a cervical length > or = 3.5 cm. This difference was statistically significant (P < 0.05). The sensitivity, specificity, positive predictive value, and negative predictive value of cervical lengths <3.5 cm to predict delivery prior to 33 gestational weeks was 67%, 94%, 67%, and 94%, respectively. CONCLUSIONS: Measurement of cervical length in triplet pregnancies before fetal reduction provides useful predictive information on the risk for preterm delivery.     

How to identify twins at low risk of spontaneous preterm delivery.

OBJECTIVE: The aim of this study was to evaluate transvaginal sonographic assessment of cervical length at 23 weeks as a screening test for spontaneous preterm delivery in order to define a cut-off value that could be used to select twin pregnancies at low risk of spontaneous preterm delivery. METHODS: In a prospective multicenter study of 383 twin pregnancies included before 14 + 6 weeks a cervical scan with measurement of the cervical length was performed at 23 weeks' gestation. The results were blinded for the clinicians if the cervical length was > or = 15 mm. The rates of spontaneous delivery at different cut-off levels of cervical length were determined. RESULTS: Eighty-nine percent of the twins had dichorionic placentation and 58% were conceived after assisted reproduction. The rate of spontaneous preterm delivery was 2.3% (1.5% for dichorionic (DC) and 9.1% for (MC) monochorionic twins) before 28 weeks and 18.5% (17.1% for DC and 29.5% for MC twins) before 35 weeks. The screen-positive rate was 5% for a cervical length < or = 20, 7-8% at < or = 25, 16-17% at < or = 30 and 34-48% at < or = 35 mm depending on chorionicity. The false-negative rate (1 - negative predictive value) ranged from 1.2% at 28 weeks to 18.6% at 35 weeks for all twins. Receiver-operating characteristics curves showed that the sensitivity increased with declining gestational age with cut-off levels of highest accuracy at 21 mm for 28 weeks and 29 mm for 33 weeks. CONCLUSIONS: Cervical length measurement at 23 weeks of gestation is a good screening test for predicting twins at low risk of preterm and very preterm delivery, especially in DC twins. The present results suggest that a cut-off of 25 mm should be recommended.     

Cervical length in the early second trimester for detection of triplet pregnancies at risk for preterm birth.

OBJECTIVE: Preterm triplet delivery is common and has a tremendous impact on neonatal mortality and morbidity. We aimed at assessing early second-trimester cervical length as a means of detecting triplet pregnancies at risk for preterm birth. METHODS: Cervical length was measured in triplet pregnancies during weeks 14 to 20. Cervical length of less than 25 mm was used as a cutoff to divide individuals into 2 groups. Perinatal outcome parameters were compared between the 2 groups and included gestational age at delivery, birth weights, and neonatal intensive care unit admission rates. Sensitivity, specificity, and positive and negative predictive values were calculated for cervical length as a screening method for preterm birth. RESULTS: We evaluated 36 triplets during weeks 14 to 20. Cervical length of less than 25 mm was measured in 14 (group I), 12 of which were delivered before 32 weeks (mean +/- SD, 28.4 +/- 3.1 weeks). Four of 22 women with cervical length of greater than 25 mm (group II) had delivery before 32 weeks (mean, 30.1 +/- 1.8 weeks). The mean gestational age at delivery for all parturients from group II was 33.1 +/- 2.1 weeks (P < .05). Group I neonates had lower birth weights (972 versus 1889 g; P < .001) and higher rates of low 5-minute Apgar scores and neonatal intensive care unit admissions compared with group II neonates. The sensitivity of a shorter cervix as a predictor of preterm labor was 75%, with specificity of 90%, a positive predictive value of 83%, and a negative predictive value of 81%. CONCLUSIONS: Cervical length of less than 25 mm at 14 to 20 weeks' gestation is associated with preterm delivery and adverse perinatal outcome in triplet pregnancies.     

Cervical length and funneling at 23 weeks of gestation in the prediction of spontaneous early preterm delivery.

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.     

Prediction of preterm birth by second trimester cervical sonography in twin pregnancies.

OBJECTIVES: To determine the predictive value of sonographic cervical length and of funneling for spontaneous preterm delivery (PTD) in twin pregnancies under 26 weeks' gestation. METHODS: Women with twin pregnancies were studied prospectively with transvaginal or translabial ultrasound of the cervix from 18 to 26 weeks' gestation. Exclusion criteria were: signs of preterm labor, prophylactic cervical cerclage, placenta previa, or severe congenital fetal anomaly. The primary outcome was spontaneous preterm birth at < 35 weeks' gestation. RESULTS: Sixty-five twin pregnancies were analyzed, of which 23% (15/65) delivered preterm. Cervical ultrasound examination was performed by 22 weeks' gestation in 75% and by 24 weeks' gestation in 91% of women. Cervical length < or = 25 mm and < or = 30 mm was associated with sensitivities of 27% and 53%, respectively, and with 67% and 62% rates of PTD, respectively (R.R. 4.6, C.I. 2.0-10.3 and R.R. 3.6, C.I. 1.6-7.8, respectively). A cervical length > 35 mm was associated with only a 4% rate of PTD (R.R 0.13; C.I. 0.02-0.93). Of 10 women (15%) with any cervical funneling, 70% delivered preterm, all under 32 weeks' gestation. By logistic regression analysis, both short cervix < or = 30 mm and any funneling were strongly predictive of PTD. CONCLUSIONS: Both cervical length < or = 30 mm and cervical funneling in twin pregnancies under 26 weeks' gestation are independently and strongly associated with high risk for preterm birth. A long cervix, of length > 35 mm, is associated with very low risk (4%) for preterm birth.     

Predicting preterm delivery in asymptomatic patients with prior preterm delivery by measurement of cervical length and phosphorylated insulin-like growth factor-binding protein-1.

OBJECTIVE: To evaluate the efficacy of cervical length measurement in combination with a bedside assessment of phosphorylated insulin-like growth factor-binding protein-1 (phIGFBP-1) as a predictor of preterm delivery in asymptomatic pregnant women with a history of preterm birth. METHODS: Cervical length was measured using transvaginal sonography at 22-24 weeks of gestation in 105 singleton pregnancies and a rapid strip test was performed to detect phIGFBP-1 in cervical secretions from 24 to 34 weeks. Receiver-operating characteristics (ROC) curves were constructed to compare the performance of phIGFBP-1 at different gestational ages, and cervical length at 22-24 weeks, in predicting preterm delivery. RESULTS: The rate of spontaneous delivery before 37 and 34 weeks was 23.8% and 11.4%, respectively. Women with cervical lengths less than 20 mm had a risk of spontaneous preterm delivery before 34 and 37 weeks of 43.5% and 69.6%, respectively. The performance of phIGFBP-1 levels as a predictor of preterm delivery was significantly higher when the test was carried out at 30 weeks' gestation. Cervical assessment in combination with phIGFBP-1 at 30 weeks had the steepest ROC curve (area under the curve=0.93; 95% CI, 0.88-0.98, P<0.001). CONCLUSION: Both cervical length and phIGFBP-1 measurement are useful in the prediction of preterm delivery in patients with a history of preterm birth and the combined method of measuring cervical length at 22-24 weeks and phIGFBP-1 at 30 weeks improves upon either method used alone.     

Ultrasound examination at 37 weeks' gestation in the prediction of pregnancy outcome: the value of cervical assessment.

OBJECTIVE: To examine the potential value of routine measurement of cervical length in singleton low-risk pregnancies at 37 weeks of gestation in the prediction of onset and outcome of labor. METHODS: Cervical length was measured by transvaginal sonography at 37 weeks in 1571 singleton low-risk pregnancies. Outcome measures were gestation at spontaneous onset of labor, post-term delivery, duration of labor and mode of delivery. RESULTS: The median cervical length at 37 weeks was 30 mm and there was a significant association between cervical length and gestation at delivery, which increased from a mean of 38 weeks for cervical length of 10 mm to 41 weeks for cervical length of 35 mm. The incidence of delivery after 40 weeks and 10 days was 296 (18.8%) and the incidence increased with cervical length at 37 weeks from 0% to 6%, 35% and 68% for respective cervical lengths of < 20, 21-30, 31-40 and 41-50 mm. In the pregnancies with spontaneous onset of labor the incidence of Cesarean section for failure to progress increased from 3.6% to 6.0%, 6.4% and 11.8% for cervical lengths of < 20, 21-30, 31-40 and 41-50 mm, respectively. In the pregnancies requiring induction for post-term the incidence of Cesarean section for failed induction or failure to progress increased from 7.5% to 20.1% to 25.0% for cervical lengths of 21-30, 31-40 and 41-50 mm, respectively. CONCLUSION: Measurement of cervical length at 37 weeks can define the likelihood of spontaneous delivery before 40 weeks and 10 days and the risk of Cesarean section in those requiring induction for prolonged pregnancy.     

Does cervical length at 13-15 weeks' gestation predict preterm delivery in an unselected population?

OBJECTIVE: To assess the role of early mid-trimester cervical length measurement as a predictor of spontaneous preterm birth in an unselected population. METHODS: In this prospective study, unselected, asymptomatic, Caucasian women with singleton pregnancies underwent standardized transvaginal ultrasonographic (TVS) cervical length measurement at 13-15 weeks' gestation as a screening test for preterm delivery (PTD). Women with multiple gestations, iatrogenic PTD, and previous cervical conization were excluded. The primary outcome measures were spontaneous PTD at < 37 and < 34 weeks. The correlation between cervical length and previous obstetric history was evaluated. RESULTS: A total of 2469 patients met the inclusion criteria. The mean gestational age at cervical assessment was 14 + 2 weeks. The mean gestational age at delivery was 40 + 0 weeks. The rate of spontaneous deliveries before 37 weeks' gestation was 1.7%. In 0.2% the delivery occurred before 34 weeks' gestation. The mean +/- standard deviation cervical length for the entire population was 44.2 +/- 5.4 mm. No difference was observed between cervical length in women that delivered at term and those that delivered either before 37 or before 34 weeks' gestation. Previous obstetric history (prior preterm birth, previous miscarriages and terminations, and parity) did not affect cervical length at 14 weeks of gestation. CONCLUSIONS: Performed at 14 weeks' gestation, TVS measurement of the cervical canal length to predict spontaneous PTD is not a reliable screening procedure.     

Elective cerclage vs. ultrasound-indicated cerclage in high-risk pregnancies.

OBJECTIVE: To compare pregnancy outcome after elective vs. ultrasound-indicated cervical cerclage in women at high risk of spontaneous mid-trimester loss or early preterm birth. METHODS: This was a retrospective study comparing two management strategies in women with singleton pregnancies who had at least one previous spontaneous delivery at 16-33 weeks of gestation. One group was managed by the placement of an elective cerclage at 12-16 weeks and the other group had transvaginal ultrasound examinations of the cervix at 12-15+6, 16-19+6, and 20-23+6 weeks and cervical cerclage was carried out if the cervical length was 25 mm or less. RESULTS: A total of 90 patients were examined, including 47 that were managed expectantly and 43 treated by elective cerclage. In the expectantly managed group, 59.6% (28/47) required a cervical cerclage. We excluded from further analysis three patients who were lost to follow-up and three because of fetal death or iatrogenic preterm delivery. Miscarriage or spontaneous delivery before 34 weeks' gestation occurred in 14.6% (6/41) of the elective cerclage group, compared with 20.9% (9/43) in the expectantly managed group (chi2 = 0.219, P = 0.640). CONCLUSION: In women at increased risk of spontaneous mid-trimester or early preterm delivery, a policy of sonographic surveillance followed by cervical cerclage in those with a short cervix reduces the need for surgical intervention without significantly increasing adverse pregnancy outcome.     

Prediction of preterm delivery in twin pregnancy: a prospective, observational study of cervical length and fetal fibronectin testing.

OBJECTIVE: To evaluate prospectively cervical length measurements and fetal fibronectin detection as predictors of spontaneous preterm delivery in an unselected population of twin pregnancies. METHODS: Transvaginal ultrasound assessments of cervical length were performed serially at 18, 24, 28 and 32 weeks' gestation. Receiver-operating characteristic curves were generated at each time point to determine the optimal cut-off for cervical length and rate of change in cervical length in the prediction of preterm delivery (< 35 weeks). A bedside assay for the detection of fetal fibronectin in the maternal vaginal secretions was performed prior to cervical length measurements from 24 weeks. Likelihood ratios (LRs) were used to assess the performance of each test. RESULTS: The spontaneous preterm delivery rate was 16.5% in 91 studied twin pregnancies. A cervical length /= 2.5 mm per week between 18 and 28 weeks' gestation also predicted preterm delivery (LR+ 10.8, sensitivity 16.7%). There was no relationship between the detection of fetal fibronectin and preterm delivery. CONCLUSIONS: This study confirms the value of transvaginal ultrasound assessment of cervical length as a predictor of preterm delivery in twin pregnancies. However, the poor sensitivity of this test makes it unsuitable as a single predictor of preterm delivery. Fetal fibronectin testing does not identify twin pregnancies destined to deliver prematurely.     

Sonographic measurement of cervical length in threatened preterm labor in singleton pregnancies with intact membranes.

OBJECTIVES: To predict when delivery will occur, within 48 h and 7 days of presentation and before 35 weeks' gestation in women presenting with threatened preterm labor. METHODS: Sonographic measurement of cervical length was carried out in 510 women with singleton pregnancies presenting with threatened preterm labor and intact membranes at 24 to 33 + 6 weeks of gestation. The measurement was not taken into account in the subsequent management of the pregnancies. The outcome measures were delivery within 48 h and 7 days of presentation and delivery before 35 weeks. RESULTS: The median gestation at presentation was 30 + 1 (range, 24 to 33 + 6) weeks and the median cervical length was 25 (range, 1-51) mm. Delivery within 48 h of presentation occurred in 21 (4.1%) cases, delivery within 7 days occurred in 43 (8.4%) and delivery before 35 weeks occurred in 76 (14.9%). Logistic regression analysis demonstrated that the only significant independent predictor of delivery within 48 h was cervical length (odds ratio (OR), 0.73; 95% CI, 0.65-0.81) and for delivery within 7 days the independent predictors were cervical length (OR, 0.69; 95% CI, 0.63-0.76) and vaginal bleeding (OR, 19.42; 95% CI, 3.87-97.4). In the subgroup of women who did not deliver within 7 days of presentation, the incidence of delivery before 35 weeks was 7.1% (33 of 467) and the only significant independent predictor of such delivery was cervical length (OR, 0.92; 95% CI, 0.88-0.96, P < 0.0001). There was no significant independent contribution to any of the outcome measures from ethnic group, maternal age, gestational age, body mass index, parity, cigarette smoking or use of tocolytics. CONCLUSIONS: In women with threatened preterm labor sonographic measurement of cervical length helps to distinguish between true and false labor and to predict early preterm delivery.     

Does transvaginal sonographic measurement of cervical length before 14 weeks predict preterm delivery in high-risk pregnancies?

OBJECTIVE: To determine whether high-risk patients manifest cervical length < 25 mm on transvaginal ultrasound before 14 weeks of gestation, and if this finding is predictive of preterm delivery. METHODS: Asymptomatic pregnancies at high risk for preterm birth were followed prospectively from 10 + 0 weeks to 13 + 6 weeks with transvaginal sonographic measurement of the cervix. A cervical length < 25 mm was considered a short cervix at this gestational age and at the follow-up ultrasound examinations, performed between 14 and 24 weeks. The primary outcome was preterm birth at < 35 weeks of gestation. RESULTS: One hundred and eighty-three pregnancies met the study criteria and were included in the analysis. Only 10 (5%) patients had a cervix < 25 mm before 14 weeks. The sensitivity, specificity and positive and negative predictive values of a short cervix were 14%, 97%, 50%, and 82%, respectively (relative risk, 2.8; 95% confidence interval, 1.4-5.6). The mean transvaginal sonographic cervical length before 14 weeks of gestation was 33.7 +/- 6.9 mm in pregnancies which delivered preterm (n = 36), and 35.0 +/- 6.8 mm in those delivering at term (n = 147) (P = 0.3). Follow-up transvaginal ultrasound examination of the cervix to 24 weeks revealed that the average gestational age at which a short cervix was detected was 18.7 +/- 2.9 weeks. CONCLUSION: A cervical length < 25 mm on transvaginal sonographic assessment rarely occurs before 14 weeks even in high-risk patients destined to deliver preterm; in these patients cervical changes predictive of preterm birth develop mostly after this gestational age.     

Cervical length at 11-14 weeks' and 22-24 weeks' gestation evaluated by transvaginal sonography, and gestational age at delivery.

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 prospective 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.     

The cervix as a predictor of preterm delivery in 'at-risk' women.

OBJECTIVE: To examine the relationship between ultrasound-determined cervical status and pregnancy outcome in women 'at-risk' of spontaneous preterm delivery. DESIGN: A prospective cohort study of 120 pregnant women considered to be 'at-risk' of spontaneous preterm delivery by their clinician. Transvaginal ultrasound of the cervix was used to assess overall cervical length, closed endocervical canal length, diameter and internal os dilatation in the second trimester. The main outcome measure was occurrence of spontaneous preterm birth (< 34 and < 37 weeks of gestation). RESULTS: The overall preterm delivery rate (< 37 weeks gestation) in these women was 35% (n = 42) with 20% (n = 24) delivering < 34 weeks gestation. Of the 71 women with a normal cervix, 8 (11%) delivered < 34 weeks, whereas of the 49 women with an abnormal cervix, 16 (33%) delivered < 34 weeks (RR 2.90; 95% CI 1.35-6.24). Using linear regression, closed endocervical canal length of < 21 mm before 20 weeks is associated with delivery < 34 weeks in 95% of women, and with delivery < 37 weeks in 95% of women if the canal length is < 33 mm. Logistic regression showed closed endocervical canal length to be the only significant factor in those women who delivered < 34 weeks after controlling for possible confounders. CONCLUSIONS: A strong relationship is demonstrated between cervical status and pregnancy outcome, particularly the cervical findings before 20 and 24 weeks of gestation. The length of the closed portion of the endocervical canal is the best predictor. A beneficial effect of this approach to 'at-risk' women is the reduction in unnecessary interventions in those with normal cervical findings.     

The use of a variable cut-off value of cervical length in women admitted for preterm labor before and after 32 weeks.

OBJECTIVE: To determine whether the optimal cut-off value to predict low risk of preterm delivery in women admitted for preterm labor should be adjusted for gestational age. METHODS: A cohort of 333 women with singleton pregnancies admitted with preterm labor and intact membranes between 24 and < 36 weeks' gestation was studied. The women were categorized according to prematurity into one of two groups: those admitted at < 32 weeks (Group 1, very preterm) and those admitted at >or= 32 weeks (Group 2, preterm). Transvaginal ultrasound was performed 24-48 h after admission and cervical length measured. The predictive value of different cut-off points was explored. Outcome variables were spontaneous preterm delivery within 7 days of admission and delivery at < 34 weeks. RESULTS: The mean ( +/- SD) gestational ages at admission and delivery were 31.9 ( +/- 2.6) and 37.5 ( +/- 2.2) weeks, respectively, and the mean ( +/- SD) cervical length was 30.4 ( +/- 8.9) mm. The rates of spontaneous delivery within 7 days and at < 34 weeks were 6.3 and 7.0%, respectively. The cut-off value of 15-mm cervical length showed a sensitivity, negative predictive value and false positive rate for delivery within 7 days of 0, 96.5 and 2.7% in the very preterm group, and 35.3, 94.6 and 4% in the preterm group, respectively. For a cut-off point of 25 mm, these values were 75, 99 and 14.3%, and 70.6, 96.8 and 24.5%. CONCLUSIONS: The predictive value of different cut-off points of cervical length is similar at different gestational ages. However, the higher false positive rate after 32 weeks' gestation might justify the adoption of gestational-age related cut-off values in clinical protocols. In women admitted at < 32 weeks' gestation, a cut-off point of 25 mm may be used to predict a low risk of preterm delivery, whereas in women admitted at 32 weeks or later, 15 mm might be more appropriate. Published by John Wiley & Sons, Ltd.     

Dynamic cervical change: is real-time sonographic cervical shortening predictive of preterm delivery in patients with symptoms of preterm labor?

OBJECTIVES: To determine prospectively if dynamic cervical change (spontaneous real-time cervical shortening) is predictive of preterm delivery at < 37 weeks' gestation in patients with symptoms of preterm labor. METHODS: This was a prospective study of patients at 23-34 weeks' gestation who were symptomatic for preterm labor. Patients underwent a 10-min real-time sonographic cervical length assessment with measurements taken at 1-min intervals. The presence or absence of dynamic cervical change, defined as real-time changes in cervical length observable to the naked eye of the sonologist during the examination, was recorded. Gestational age at delivery was obtained from medical records. Preterm delivery was defined as delivery at < 37 weeks' gestation. Dynamic cervical change and initial and minimum cervical lengths were assessed for prediction of preterm delivery. RESULTS: Seventy-six patients were enrolled, and 66 were available for outcome analysis. Thirty-one patients (47%) exhibited dynamic cervical change. Patients with dynamic change had shorter initial cervical lengths (27 mm vs. 36 mm, P = 0.001), shorter minimum cervical lengths (20 vs. 33 mm, P < 0.001) and larger changes in cervical length during the examination period (10 vs. 4 mm, P < 0.001). In the subgroup of patients with an initial cervical length > 30 mm, those with dynamic change delivered earlier than did those without dynamic change (36.8 vs. 38.6 weeks, P = 0.02), and a higher percentage delivered preterm (27% vs. 11%, odds ratio (OR), 3.0 (0.5-17.0)). Multivariate analysis showed that minimum cervical length was a better predictor of preterm delivery than was initial cervical length. CONCLUSIONS: Dynamic cervical change occurs frequently in association with shortened cervical length. In patients with longer initial cervical lengths, dynamic change may increase the risk for preterm delivery. When dynamic change is noted in a patient with preterm labor symptoms, use of the minimum cervical length observed may be better compared with initial cervical length for determining preterm delivery risk.     

Cervical changes in twin pregnancies observed by transvaginal ultrasound during the latter half of pregnancy: a longitudinal, observational study.

OBJECTIVE: To determine what constitutes normal cervical changes in twin gestations during the latter half of pregnancy, and whether there are differences in the pattern of cervical change between women expecting twins giving birth at term (> or = 36 completed gestational weeks, GW) and preterm. METHODS: Twenty women (12 nulliparous, eight parous) expecting twins were examined with transvaginal ultrasound every week from 24 GW until delivery. Cervical length and width were measured, the inner cervical os was assessed as being closed or open, and any dynamic cervical changes were noted. Examination results were unavailable to the staff involved in the care of the women. RESULTS: Eight women (40%) delivered preterm spontaneously at 32-35 GW. Cervical length remained unchanged ( approximately 10 mm) in one woman, who delivered preterm. It decreased in the remaining 19 women. The median shortening rate for women manifesting a continuous shortening of the cervix was 2.9 (0.8-5.2) mm/week in women giving birth preterm vs. 1.8 (0.8-2.4) mm/week in those who gave birth at term (P = 0.08). Median cervical length at the first examination was similar in women who delivered preterm and at term (39 vs. 41 mm), but at 32 GW the cervix was shorter in women who delivered preterm (median, 18 vs. 31 mm, P = 0.02). Cervical width remained unchanged in 63% (5/8) of the women who delivered preterm vs. 8% (1/12) of those who gave birth at term (P = 0.02). The cervix became wider in the remaining women. Median cervical width at the first examination was similar in women who delivered preterm and at term (38 vs. 38 mm), but in women who delivered preterm the cervix was thinner at 0-6 days before spontaneous start of labor (median, 40 vs. 48 mm, P = 0.07). An opening of the inner cervical os was seen < or = 27 GW in 88% (7/8) of the women who delivered preterm vs. 17% (2/12) of those who delivered at term (P = 0.006), the corresponding figures for dynamic changes being 63% (5/8) vs. 17% (2/12) (P = 0.06). Dynamic changes were seen in a greater proportion of the examinations in women who delivered preterm (median, 25% vs. 4%, P = 0.07). CONCLUSIONS: The pattern of cervical changes from 24 GW to delivery differs between twin pregnancies delivering preterm (at 32-35 GW) and at term (> or = 36 GW). In twin pregnancies delivered preterm cervical shortening is more rapid, the cervix does not broaden to the same extent as in twins delivered at term, an open inner cervical os and dynamic cervical changes are seen earlier in gestation, and dynamic cervical changes are seen more often. Cervical changes in women with twins who give birth as early as at 24-31 GW may be different.     

Sonographic cervical length in singleton pregnancies with intact membranes presenting with threatened preterm labor.

OBJECTIVE: Less than 10% of women presenting with preterm contractions progress to active labor and delivery. This study investigates whether cervical length measurements by ultrasound can discriminate between true and false labor in women presenting with threatened preterm labor. METHODS: Cervical length was measured by transvaginal ultrasound in 253 women with singleton pregnancies presenting with painful uterine contractions at a median age of 31 (range, 24-35) weeks of gestation. Women presenting in active labor, defined by the presence of cervical dilatation of >or = 3 cm, those with ruptured membranes and those that underwent prior or subsequent cervical cerclage were excluded from the study. The clinical management was determined by the attending obstetrician without taking into account the cervical length. Primary outcome of the study was delivery within 7 days of presentation based on the results of randomized studies on the use of tocolytics in women with preterm labor that reported a prolongation of pregnancy by 7 days. RESULTS: Delivery within 7 days of presentation occurred in 21/253 (8.3%) pregnancies and this was inversely related to cervical length. Receiver-operating characteristics (ROC) curves established a cervical length of 15 mm as the most relevant cut-off level for the prediction of preterm delivery within 7 days. In 217 cases the cervical length was > or = 15 mm and only four of these (1.8%) delivered within 7 days. In the 36 women with cervical length < 15 mm, delivery occurred in 17 (47.2%) within 7 days. Logistic regression analysis demonstrated that significant independent contribution in the prediction of delivery within 7 days was provided by cervical length, contraction frequency at presentation, previous history of preterm delivery and vaginal bleeding. There was no significant contribution from gestation at presentation, ethnic origin, maternal age, parity, cigarette smoking or the administration of tocolysis, antibiotics or steroids. Similar results were shown in a subanalysis of 162 patients presenting at a gestational age below 32 weeks: 9/19 patients (47.4%) with a cervical length below 15 mm delivered within 7 days compared to 3/143 (2.1%) with a cervical length > or = 15 mm. Univariate as well as multivariate analyses confirmed cervical length to be a significant independent predictor of delivery within 7 days in this population. CONCLUSIONS: Sonographic measurement of cervical length helps to avoid overdiagnosis of preterm labor in women with preterm contractions and intact membranes.     

Cervical length at 18-22 weeks of gestation for prediction of spontaneous preterm delivery in Hong Kong Chinese women.

OBJECTIVE: To assess the value of a single cervical length measurement by transvaginal sonography (TVS) at the time of mid-trimester anomaly scan for predicting spontaneous preterm delivery (SPD) among Chinese women. METHODS: A prospective observational study was carried out involving 2880 subjects with singleton pregnancies and confirmed gestational age. Cervical length was measured at 18-22 weeks of gestation. RESULTS: The incidence of SPD < 34 weeks and < 37 weeks were 0.7% and 3.7%, respectively. Women with SPD < 34 weeks and SPD < 37 weeks had shorter median cervical lengths (32.6 mm and 36.2 mm, respectively) than those with term deliveries (37.6 mm) (P = 0.006 and 0.025, respectively). The predictive performance of cervical length was better for SPD < 34 weeks compared with < 37 weeks. A cervical length < or = 27 mm, which corresponded to the 4th centile, occurred in 36.8%, 62.5% and 100% of those with SPD < 34, < 30 and < 26 weeks, respectively. The positive likelihood ratio (LR) of a cervical length < or = 27 mm in predicting SPD < 34 weeks was 9.8. Using logistic regression, both short cervix and funneling were independent predictors for SPD < 34 weeks of gestation. The coexistence of funneling and a cervical length < or = 27 mm gave a positive predictive value (PPV) and LR of SPD < 34 weeks of 14.7% and 26.0, respectively. CONCLUSIONS: Mid-trimester cervical length is predictive of SPD in Chinese women. However, given the low PPV of a short cervical length, its clinical utility is still limited in low-risk populations.