Change in cervical length after cerclage as a predictor of preterm delivery

Beyond Cervical Length: Association between Postcerclage Transvaginal Ultrasound Parameters and Preterm Birth

OBJECTIVE

To assess the value of transvaginal ultrasound parameters after cerclage placement in estimating the risk of spontaneous preterm birth.

STUDY DESIGN

This is a retrospective cohort at a single tertiary care center from 2013 to 2016. Women carrying a singleton, nonanomalous fetus with cerclage in situ and at least one postcerclage transvaginal ultrasound from 16^0/7 to 25^6/7 weeks' gestation were included. In addition to abstracting maternal demographic and obstetric characteristics, two study investigators separately reviewed each of the images from the first transvaginal ultrasound after cerclage placement, masked to pregnancy outcomes. We measured the angle between the anterior uterine wall and cervical canal at the internal os and external os, closed canal length above and below the stitch, width of the anterior and posterior cervix at the level of the cerclage, and stitch distance from the cervical canal. The presence of additional ultrasound findings such as sludge and cervical funneling was also noted. The main outcomes were preterm birth < 34 weeks and preterm birth < 37 weeks. Transvaginal ultrasound parameters were compared between women with preterm birth and those without preterm birth using chi-square, Fisher's exact, and Wilcoxon's rank-sum tests, as appropriate. Log binomial regression was used to estimate the relative risk of preterm birth for all significant obstetric and ultrasound characteristics.

RESULTS

A total of 102 women met inclusion criteria: 58% had history-indicated, 20% ultrasound-indicated, and 23% exam-indicated cerclages. Of these, 28 (27.5%) women delivered at < 34 weeks' gestation, and 48 (47.0%) women delivered at < 37 weeks' gestation. Preterm birth did not vary by race, maternal age, insurance, smoking, or gestational age of the earliest prior preterm birth (for multiparous women), but women who had preterm birth were more likely to have exam-indicated cerclage. There were several transvaginal ultrasound parameters associated with preterm birth < 34 weeks and preterm birth < 37 weeks. Of these, cervical length below the stitch, stitch distance from the cervical canal, straight cervical canal, funneling to or past the stitch, and presence of sludge had the greatest effect sizes.

CONCLUSION

Rates of preterm birth are high postcerclage. In addition to measuring cervical length, utilization of postcerclage transvaginal ultrasound to evaluate the location of the cerclage within the cervix, the curvature of the cervical canal, and the presence of funneling and sludge may help identify women who are at the highest risk for preterm birth.

Evidence that antibiotic administration is effective in the treatment of a subset of patients with intra-amniotic infection/inflammation presenting with cervical insufficiency

BACKGROUND

Cervical insufficiency is a risk factor for spontaneous midtrimester abortion or early preterm birth. Intra-amniotic infection has been reported in 8-52% of such patients and intra-amniotic inflammation in 81%. Some professional organizations have recommended perioperative antibiotic treatment when emergency cervical cerclage is performed. The use of prophylactic antibiotics is predicated largely on the basis that they reduce the rate of complications during the course of vaginal surgery. However, it is possible that antibiotic administration can also eradicate intra-amniotic infection/inflammation and improve pregnancy outcome.

OBJECTIVE

To describe the outcome of antibiotic treatment in patients with cervical insufficiency and intra-amniotic infection/inflammation.

STUDY DESIGN

The study population consisted of 22 women who met the following criteria: (1) singleton pregnancy; (2) painless cervical dilatation of >1 cm between 16.0 and 27.9 weeks of gestation; (3) intact membranes and absence of uterine contractions; (4) transabdominal amniocentesis performed for the evaluation of the microbiologic and inflammatory status of the amniotic cavity; (5) presence of intra-amniotic infection/inflammation; and (6) antibiotic treatment (regimen consisted of ceftriaxone, clarithromycin, and metronidazole). Amniotic fluid was cultured for aerobic and anaerobic bacteria and genital mycoplasmas, and polymerase chain reaction for Ureaplasma spp. was performed. Intra-amniotic infection was defined as a positive amniotic fluid culture for microorganisms or a positive polymerase chain reaction for Ureaplasma spp., and intra-amniotic inflammation was suspected when there was an elevated amniotic fluid white blood cell count (≥19 cells/mm³) or a positive rapid test for metalloproteinase-8 (sensitivity 10 ng/mL). For the purpose of this study, the "gold standard" for diagnosis of intra-amniotic inflammation was an elevated interleukin-6 concentration (>2.6 ng/mL) using an enzyme-linked immunosorbent assay. The results of amniotic fluid interleukin-6 were not available to managing clinicians. Follow-up amniocentesis was routinely offered to monitor the microbiologic and inflammatory status of the amniotic cavity and fetal lung maturity. Treatment success was defined as resolution of intra-amniotic infection/inflammation or delivery ≥34 weeks of gestation.

RESULTS

Of 22 patients with cervical insufficiency and intra-amniotic infection/inflammation, 3 (14%) had microorganisms in the amniotic fluid. Of the 22 patients, 6 (27%) delivered within 1 week of amniocentesis and the remaining 16 (73%) delivered more than 1 week after the diagnostic procedure. Among these, 12 had a repeat amniocentesis to assess the microbial and inflammatory status of the amniotic cavity; in 75% (9/12), there was objective evidence of resolution of intra-amniotic inflammation or intra-amniotic infection demonstrated by analysis of amniotic fluid at the time of the repeat amniocentesis. Of the 4 patients who did not have a follow-up amniocentesis, all delivered ≥34 weeks, 2 of them at term; thus, treatment success occurred in 59% (13/22) of cases.

CONCLUSION

In patients with cervical insufficiency and intra-amniotic infection/inflammation, administration of antibiotics (ceftriaxone, clarithromycin, and metronidazole) was followed by resolution of the intra-amniotic inflammatory process or intra-amniotic infection in 75% of patients and was associated with treatment success in about 60% of cases.

The predictive value of sequential cervical length screening in singleton pregnancies after cerclage: a retrospective cohort study

Background

There are few valid predictors for preterm delivery after cerclage. Experience with a screening program that included four sequential cervical length measurements in singleton pregnancies after cerclage is reviewed.

Methods

In this retrospective cohort study, 88 singleton pregnancies after cerclage were included. Cervical length (CL) measurements were performed perioperatively and at weeks 16 + 0, 18 + 0, 20 + 0, and 22 + 0 by transvaginal ultrasound. Predictive factors for early preterm delivery included patient characteristics, obstetric history and CL measurements and were analyzed separately for women with ultrasound-indicated cerclage and those with history-indicated cerclage. Women with emergency cerclage were excluded.

Results

In women with delivery <35 weeks, CL declined from the 16 + 0 to the 22 + 0 weeks of gestation (p = 0.009). In univariate analysis, all CL measurements were predictive for delivery <35 weeks in women who underwent ultrasound-indicated cerclage and in women who received a history-indicated cerclage, whereas in multivariate analysis only CL three to six days after cerclage remained significant (odds ratio 0.85, 95 % CI 0.73–0.98). In women with ultrasound-indicated cerclage, optimized cut-off was ≤20 mm (specificity 83.8 %, sensitivity 84.2 %).

Conclusions

CL measured three to six days after cerclage placement provides the best information about the risk for delivery <35 weeks.

Post-cerclage ultrasonographic cervical length can predict preterm delivery in elective cervical cerclage patients

Objective

To evaluate the usefulness of transvaginal ultrasound measurements of cervical length before and after elective prophylactic cervical cerclage in predicting preterm delivery before 32 weeks of gestation.

Methods

Women who underwent an elective cerclage operation at 14 to 19 weeks of gestation and who delivered between January 2004 and December 2009 were enrolled in this study (n=52). Ultrasonography was performed to measure cervical length before and after cerclage. The primary outcome was defined as preterm delivery before 32 weeks of gestation. A receiver operating characteristic curve was used to determine the most discriminating cut-off values of ultrasonographic cervical parameters predictive of preterm delivery before 32 weeks of gestation.

Results

Among the 52 patients studied, ten delivered before 32 weeks of gestation. Among the ultrasonographic cervical parameters compared, only the cervical length after cerclage was significantly different (shorter) in patients who delivered before 32 weeks of gestation (P=0.037) compared to that of those who delivered after 32 weeks of gestation in univariate and multivariate analyses (odds ratio, 0.402; 95% confidence interval, 0.174 to 0.925; P=0.021). The receiver operating characteristic curve showed that a cervical length of 25 mm or less after cerclage was predictive of preterm delivery before 32 weeks of gestation (area under curve, 0.71; 95% confidence interval, 0.56 to 0.87; P=0.029) with a sensitivity of 91.0% and a specificity of 30.0%.

Conclusion

Patients with a cervical length less than 25 mm after elective cerclage may be at higher risk of preterm delivery before 32 weeks of gestation.

Reinforcing cerclage for a short cervix at follow-up after the primary cerclage procedure

OBJECTIVE

To determine whether a reinforcing cerclage (RC) for a short cervix measured after the primary cerclage procedure prolonged pregnancy.

METHODS

We conducted a retrospective cohort study of 157 women with singleton gestations who underwent cerclage for standard indications. Women were grouped according to cervical length (CL) at the time of follow-up 1-2 weeks after the initial cerclage placement: ≥25 mm (106 women) and <25 mm with (20 women) or without RC (31 women). Gestational age (GA) at delivery was compared by ANOVA. Survival risk analysis was applied to model GA at delivery adjusted for indication and CL before and after the first cerclage.

RESULTS

Women with CL ≥25mm delivered later than women with CL < 25mm after the first cerclage (p < 0.01). RC did not delay delivery for women with CL < 25 mm (p = 0.17) after the primary procedure. Indication for the primary cerclage (p < 0.01) and CL (p < 0.01) after the primary cerclage were the best predictors for GA at delivery.

CONCLUSION

Placement of RC for short cervix did not prolong duration of pregnancy, GA at delivery or modify the probability of preterm birth.

Does the rate of cervical shortening after cerclage predict preterm birth?

OBJECTIVE

The objective of this study is to evaluate whether the rate of cervical shortening after cerclage can predict spontaneous preterm birth (SPTB).

METHODS

Women who had cervical length (CL) assessments after cerclage placement were identified. The rate of cervical shortening and its relationship with SPTB was established using a generalized linear regression model. Secondary outcomes included relationship between cervical shortening and risk of SPTB in those with a post-cerclage CL <25 mm versus ≥25 mm at 18-20 weeks; and the rate of cervical shortening in women who delivered preterm compared with those who delivered at term.

RESULTS

One hundred thirty-four patients were included and 30 (22.4%) delivered at <36 weeks. A rate of cervical shortening of 1 mm/week conferred a risk of SPTB of 22%. Among women with cerclage who had a CL <25 mm at 18-20 weeks, 1 mm/week of cervical shortening was associated with a 59% risk of SPTB. Patients with cerclage who delivered at term had a slower rate of cervical shortening compared to those who delivered preterm (0.62 mm versus 1.40 mm per week, p = 0.008).

CONCLUSIONS

The rate of cervical shortening after cerclage placement is associated with the risk of SPTB. Sonographic surveillance of the rate of cervical shortening may be useful in assessing risk for SPTB in patients with cerclage.

Factors associated with spontaneous preterm birth risk assessed by transvaginal ultrasound following cervical cerclage

OBJECTIVE

To determine the predictive value of various cervical length measurements postcerclage for the outcome of preterm birth following both elective and rescue cerclage.

MATERIALS AND METHODS

Over a five-year period, we identified 59 women who had a transvaginal cerclage inserted followed by serial cervical length measurement. Of these, 18 were elective cerclages placed at 14 weeks of gestation on the basis of a history of cervical insufficiency and 41 were rescue cerclages performed at gestations ranging from 17 to 23 weeks following a diagnosis of shortened cervix on ultrasound. The women were asymptomatic throughout.

RESULTS

There was a strong correlation between cervical length postcerclage and gestation at delivery. For both groups, preterm birth could be predicted by the total cervical length. In the rescue cerclage group, the change in cervical length was predictive, with positive changes associated with later gestation at delivery. The presence of funnelling was predictive of preterm birth in the elective cerclage group only.

CONCLUSION

Transvaginal cervical length measurement is useful in the prediction of preterm birth postcerclage placement. Serial cervical length measurement postcerclage may assist with timely addition of interventions such, progesterone and antenatal cortico steroids for fetal lung maturation.

Infection and smoking are associated with decreased plasma concentration of the anti-aging protein, α-klotho

OBJECTIVE

The objective of this study was to determine whether maternal plasma concentrations of soluble α-klotho are different between women with microbial invasion of the intra-amniotic cavity (MIAC) and those without MIAC among preterm labor and intact membranes (PTL) or preterm prelabor rupture of membranes (pPROM).

METHODS

A cross-sectional study was conducted to include women in the following groups: i) PTL with MIAC (n=14); ii) PTL without MIAC (n=79); iii) pPROM with MIAC (n=30); and iv) pPROM without MIAC (n=33). MIAC was defined as a positive amniotic fluid culture for microorganisms (aerobic/anaerobic bacteria or genital mycoplasmas). Amniotic fluid samples were obtained within 48 h of maternal blood collection. Plasma concentration of soluble α-klotho was determined by ELISA.

RESULTS

i) The median plasma concentration (pg/mL) of soluble α-klotho was significantly lower in patients with MIAC than in those without MIAC (787.0 vs. 1117.8; P<0.001). ii) Among patients with PTL, those with MIAC had a lower median plasma concentration (pg/mL) of soluble α-klotho than those without MIAC (787.0 vs. 1138.9; P=0.007). iii) Among patients with pPROM, those with MIAC had a lower median plasma concentration (pg/mL) of soluble α-klotho than those without MIAC (766.4 vs. 1001.6; P=0.045). iv) There was no significant difference in the median plasma concentration of soluble α-klotho between PPROM without MIAC and PTL without MIAC (1001.6 pg/mL vs. 1138.9 pg/mL, respectively; P=0.5). v) After adjustment for potential confounders (maternal age, tobacco use, gestational age at venipuncture), soluble α-klotho remained significantly associated with MIAC (P=0.02); and vi) Among patients without MIAC, smoking was significantly associated with a lower median plasma concentration soluble α-klotho than in non-smokers (794.2 pg/mL vs. 1382.0 pg/mL, respectively; P<0.001); however, this difference was not observed in patients with MIAC.

CONCLUSIONS

Intra-amniotic infection occurring at preterm gestations (regardless of membrane status) was associated with a decrease in maternal plasma concentrations of soluble α-klotho. Moreover, among patients without infection, the plasma concentration of α-klotho was lower in smokers.

Transvaginal sonographic evaluation of the cervix in asymptomatic singleton pregnancy and management options in short cervix

Preterm delivery (PTD), defined as birth before 37 completed weeks of gestation, is the leading cause of perinatal morbidity and mortality. Evaluation of the cervical morphology and biometry with transvaginal ultrasonography at 16–24 weeks of gestation is a useful tool to predict the risk of preterm birth in low- and high-risk singleton pregnancies. For instance, a sonographic cervical length (CL) > 30 mm and present cervical gland area have a 96-97% negative predictive value for preterm delivery at <37 weeks. Available evidence supports the use of progesterone to women with cervical length ≤25 mm, irrespective of other risk factors. In women with prior spontaneous PTD with asymptomatic cervical shortening (CL ≤ 25 mm), prophylactic cerclage procedure must be performed and weekly to every two weeks follow-up is essential. This article reviews the evidence in support of the clinical introduction of transvaginal sonography for both the prediction and management of spontaneous preterm labour.

Endocervical hyaluronan and ultrasound-indicated cerclage

OBJECTIVE

To investigate whether, at the time of ultrasound-indicated cerclage, the endocervical concentration of hyaluronan (HA), 27-kDa heat shock protein (HSP-27) and/or interleukin-8 (IL-8) would predict pregnancy outcome.

METHODS

Endocervical samples, obtained from 40 women undergoing ultrasound-indicated cerclage at 15 + 3 to 25 + 0 weeks' gestation, were assayed by enzyme-linked immunosorbent assay for HA, HSP-27 and IL-8. All subjects had a cervical length of < 1.5 cm or dramatic cervical length change on serial endovaginal ultrasound, no uterine contractions or tenderness, no fever and intact membranes and underwent a modified Shirodkar cerclage.

RESULTS

The median HA level was 10.0 ng/mL in the 12 women who delivered at < 37 weeks' gestation as opposed to 39.7 ng/mL in the 28 women delivering at 37-41 weeks (P = 0.017). Median HSP-27 and IL-8 concentrations were not significantly different in these groups.

CONCLUSION

A higher endocervical HA level at the time of ultrasound-indicated cerclage is associated with a longer interval before birth.

Is there value for serial ultrasonographic assessment of cervical lengths after a cerclage?

OBJECTIVE

The objective of the study was to determine the value of serial ultrasonographic cervical length (CL) measurements after cerclage to predict preterm delivery.

STUDY DESIGN

Retrospective ultrasonographic and outcome data from singleton pregnancies with cerclage were reviewed. Using transvaginal ultrasound (TVS), overall CL obtained before cerclage placement, 2 weeks after cerclage, and before delivery were compared between women who delivered preterm (less than 37 weeks) and term. The overall CL including CL above (CLA) and below the cerclage (CLB) were compared using the SAS program.

RESULTS

Cerclage was placed at 15.7 +/- 3.6 weeks (mean +/- SD) in 57 women. The overall CL before cerclage, 2 weeks after cerclage, and the last TVS before delivery was not different in preterm and term births. The odds ratio of a measurable CLA for preterm delivery by TVS was 0.87 (0.78 to 0.95, 95% confidence interval). Thirty-two patients (56%) had absent CLA at 26.7 +/- 4.4 weeks. Of these, 16 (50%) were delivered for preterm premature rupture of membranes (PPROM) and chorioamnionitis (sensitivity of 100%, specificity of 61%, positive predictive value of 50%, and negative predictive value of 100%).

CONCLUSION

Although the overall cervical length by serial TVS after cerclage did not predict preterm birth, absent CLA is associated with preterm delivery, chorioamnionitis, and PPROM.

Role of ultrasound in screening patients at risk for preterm delivery

The ultrasound assessment of the cervix has contributed to the understanding of the pathways to preterm birth. Transvaginal ultrasound measurement of the cervix provides an objective and noninvasive tool for the evaluation of cervical status. Despite widespread use of this procedure, standardization of measurement indications, technique, and interval between examinations has not been achieved. The American College of Radiology has recently recommended that the cervix and lower uterine segment be imaged as part of every obstetric ultra-sound examination in the second trimester. These guidelines specifically suggest a search for a short cervix (less than 30 mm) or funneling. The expert panel on women's imaging further recommended evaluating the cervix sonographically on both the initial examination and all follow-up examinations for twin gestations. The American Institute of Ultrasound in Medicine guidelines indicate that evaluation of the uterus, including cervix, should be performed, but does not indicate specifically that the cervix should be measured. In contrast, the American College of Obstetricians and Gynecologists, although recognizing that cervical length assessment may be helpful in predicting the risk of preterm delivery (particularly from a negative predictive value), does not recommend routine use of cervical length measurement because of the lack of proved treatment or intervention methods. A review of the literature suggests that at the time of this writing the role of routine screening of low-risk women with cervical length assessment by ultrasound is not supported. In contrast, in women at risk for preterm delivery(eg, women with a prior history of preterm birth or women with multiple gestations) cervical length assessment may be useful for its negative predictive value. At present, however, there is no therapeutic intervention that has been proved to decrease the risk of preterm delivery in women with a documented cervix on ultrasound.

Vaginal fetal fibronectin as a predictor of spontaneous preterm delivery in the patient with cervical cerclage

OBJECTIVE

The purpose of this study was to assess the validity of vaginal fetal fibronectin as a screening test for spontaneous preterm birth in patients with cervical cerclage.

STUDY DESIGN

A historic cohort of 117 patients who underwent cervical cerclage placement between 1996 and 2002 were identified. All patients were followed up in a maternal-fetal medicine faculty practice in a university setting. Serial fetal fibronectin samples of vaginal secretions were collected every 2 to 3 weeks, starting at 22 weeks of gestation and continuing until 32 weeks or delivery, whichever came first.

RESULTS

There were 81 singleton, 23 twin, 12 triplet, and 1 quadruplet pregnancies. There were 61 ultrasound-indicated, 47 prophylactic, and 9 emergency cerclages that were placed. Most cerclages were of the modified Shirodkar type (95%) with a median gestational age at cerclage placement of 16.6 weeks. Overall, 33.3% of gestations were delivered spontaneously before 37 weeks of gestation; 17.1% of gestations were delivered spontaneously before 34 weeks. For deliveries within 2 weeks and 3 weeks of a single fetal fibronectin assessment, the test had a sensitivity of 50% and 48.3%, a specificity of 90% and 91.1%, a positive predictive value of 16.3% and 28.6%, and a negative predictive value of 97.9% and 96%, respectively. Subgroup analysis by number of fetuses (singleton, twin, and higher order multiple gestations) revealed similar values. For delivery before 34 weeks of gestation, fetal fibronectin had a sensitivity of 50%, a specificity of 78.4%, a positive predictive value of 33.3%, and a negative predictive value of 88%.

CONCLUSION

This study is the first to evaluate the use of vaginal fetal fibronectin assessments to screen for preterm birth in patients who had undergone cervical cerclage procedures. We conclude that this test has similar validity to predict spontaneous preterm delivery in these high-risk pregnancies, as in previously published cohorts.

Does cerclage location influence perinatal outcome?

OBJECTIVE

The study was undertaken to measure cerclage location within the cervix and to determine whether placement closer to the internal os is related to perinatal outcome.

STUDY DESIGN

We analyzed data collected during a randomized trial of cervical cerclage versus no cerclage that was conducted at Lehigh Valley Hospital between May 1998 and June 2001 in women with ultrasound findings of short cervix less than 25 mm or funneling between 16 and 24 weeks' gestation. Women who were randomly assigned to the cerclage arm had cervical measurements performed before cerclage, including dilation of the internal os, depth of membrane prolapse into the endocervical canal, cervical length below any funnel (distal length), and total cervical length (including any funnel). Measurements obtained after cerclage placement included the distance from external os to cerclage (A), and a repeat of the same four measurements. The distance from the external os to the cerclage (A) was divided by the total cervical length (B) and a cerclage to cervical length ratio (A/B) was calculated. The relationship between these measurements and gestational age at birth was assessed by linear regression analysis.

RESULTS

Of 150 patients enrolled, 74 received a McDonald cerclage suture. Mean distal cervical length was 1.9+/-0.9 cm before and 2.9+/-1.0 cm after cerclage (P=.001). The mean distance between the cerclage and external os (A) was 1.8+/-0.6 cm; the total cervical length after cerclage (B) was 3.6+/-0.9 cm. The mean cerclage to cervical length ratio (A/B) was 0.5+/-0.1. Linear regression analysis did not demonstrate a correlation between either the cerclage to external os measurement (A) or the cervical length ratio (A/B) and gestational age at birth (R(2)=0.0006 and 0.008, P=.8 and.6, respectively).

CONCLUSION

The length of the cervix below the level of cerclage is not related to duration of pregnancy in women treated with cerclage because of ultrasound evidence of cervical effacement.

Cervical Incompetence Prevention Randomized Cerclage Trial (CIPRACT): effect of therapeutic cerclage with bed rest vs. bed rest only on cervical length

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, randomization for therapeutic cerclage and bed rest vs. just bed rest was performed. After randomization, 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 randomly 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 randomization 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.

Cervical screening for preterm delivery

The ability of sonographic cervical length screening to detect those at risk of spontaneous preterm delivery has been extensively explored over the past few years. This applies both to high-risk and low-risk groups. Cervical length measurement appears to be superior to biochemical, microbiological or hormonal methods of screening. The screening technique has been standardized, but the cervical length for intervention and the timing and nature of intervention have not been defined. Cervical cerclage appears to be of use to prevent or arrest the progress of cervical dilation in high-risk cases, but the management of the screen-positive low-risk case has yet to be determined. Future management may be stratified according to actual cervical length, and prospective randomized trials of treatment for the short cervix are needed.

Transvaginal sonographic examination of the cervix in asymptomatic pregnant women: review of the literature

Different strategies have been developed to refine the prediction of the risk of preterm delivery in asymptomatic patients. Transvaginal sonography has been used for this reason to measure and examine the length and shape of the cervix. In this review, we focus on clinical studies involving transvaginal sonographic assessment of the cervix in asymptomatic women at high risk of preterm delivery and in the general pregnant population. Three ultrasound signs are suggestive of cervical incompetence, namely, dilatation of the internal os, sacculation or prolapse of the membranes into the cervix (with shortening of the functional cervical length) either spontaneously or induced by transfundal pressure, and short cervix in the absence of uterine contractions. Transvaginal sonography has clearly demonstrated that cerclage leads to a measurable increase in cervical length which may contribute to the success of this procedure in reducing the risk of preterm delivery. Several non-randomized interventional studies among patients with cervical incompetence have been published. They have defined a new group of patients requiring cerclage when the women show progressive cervical modifications on transvaginal sonography, while in other studies, cerclage performed on the basis of cervical changes on transvaginal sonography did not prevent premature delivery. One prospective randomized trial in asymptomatic high-risk women has shown two benefits of cerclage following indications for transvaginal sonography: (1) it would generate fewer prophylactic cerclages in high-risk women; (2) therapeutic cerclage before 27 weeks may reduce the incidence of premature delivery before 34 weeks. The risk of preterm delivery is inversely correlated with cervical length. Routine transvaginal sonography of the cervix performed between 18 and 22 weeks can help identify patients at risk of preterm delivery. However, given the low prevalence of preterm births, screening would generate either a high false-positive rate or a low sensitivity. One non-randomized interventional study among patients with a short cervix on routine ultrasound examination found a lower risk of delivery before 32 weeks in the cerclage group than in the expectant management group. However, to date, there have been no prospective randomized trials in a general population. Although evidence is still lacking, there does appear to be a benefit in performing a cerclage rather than continuing with expectant management in cases with sonographic appearance of cervical incompetence in asymptomatic women at high risk of preterm delivery. Ultrasound can be offered to reduce the indications of cerclage for cases in which the situation is uncertain. Within the general obstetric population, transvaginal sonography might help in the selection of asymptomatic but high-risk women. However, the benefit associated with cerclage for sonographic indication has not been demonstrated.