The prospects for multiple-marker screening for preterm delivery: does transvaginal ultrasound of the cervix have a central role?

Nomogram to predict the risk of preterm birth before 37 weeks and 34 weeks in pregnant women with a short cervix

OBJECTIVES

This study investigated the potential factors that predict the risk of preterm birth (PTB) in pregnancies with a short cervix. These factors were used to create nomogram, which might be highly sensitive tools to predict the incidence of PTB.

METHODS

This retrospective cohort study enrolled pregnancies with a short cervix from 1 January 2017 to 1 January 2018. The primary outcomes were preterm birth <37 and 34 weeks. Logistic regression model was used to identify potential predictors of PTB. The identified risk factors were used to establish nomograms, which were validated using the receiver operating characteristic (ROC) curve and calibration curve.

RESULTS

In the multivariate analysis, overweight or obesity, parity ≧3 times, twin pregnancy, in vitro fertilization and embryo transfer (IVF-ET), gestational age at first observation of short cervix, cervical length (CL) at first observation of short cervix, history of PTB, and autoimmune disease were found to be predictors of PTB <37 weeks, while twin pregnancy, gestational age at first observation of short cervix, CL of short cervix, history of PTB, and prepregnancy hypertension were predictors of PTB <34 weeks. The area under the ROC curve of the nomogram predicting PTB <37 weeks and PTB <34 weeks were 0.803 and 0.771, respectively. Both models showed good discrimination.

CONCLUSIONS

Gestational age at first observation of short cervix, CL of short cervix and other factors are strong predictors of PTB in pregnancies with a short cervix. Both nomograms showed good discrimination and calibration, and hence might be effective in predicting PTB for this population.

Transvaginal sonographic measurement of cervical length to predict preterm birth in asymptomatic women at increased risk: a systematic review

OBJECTIVES

To estimate the ability of cervical length measured by transvaginal ultrasonography in asymptomatic high-risk women to predict spontaneous preterm birth.

METHODS

MEDLINE, PubMed, EMBASE and the Cochrane Library were searched for articles published in any language between January 1980 and July 2006, using the keywords 'transvaginal ultrasonography' or ('cervix' and ('ultrasound' or 'ultrasonography' or 'sonography')); and ('preterm' or 'premature') and ('delivery' or 'labour/labor' or 'birth'), identifying cohort studies evaluating transvaginal ultrasonographic cervical length measurement in predicting preterm birth in asymptomatic women who were considered at increased risk (because of a history of spontaneous preterm birth, uterine anomalies or excisional cervical procedures), with intact membranes and singleton gestations. The primary analysis included all studies meeting the inclusion criteria. Secondary analyses were also performed specifically for (1) women with a history of spontaneous preterm birth; (2) those who had undergone an excisional cervical procedure; and (3) those with uterine anomalies.

RESULTS

Fourteen of 322 articles identified (involving 2258 women) met the criteria for systematic review. Cervical length measured by transvaginal ultrasonography predicted spontaneous preterm birth. The shorter the cervical length cut-off the higher the positive likelihood ratio (LR). The most common cervical length cut-off was < 25 mm. Using this cut-off to predict spontaneous preterm birth at < 35 weeks, transvaginal ultrasonography at < 20 weeks' gestation revealed LR+ = 4.31 (95% CI, 3.08-6.01); at 20-24 weeks, LR+ = 2.78 (95% CI, 2.22-3.49); and at > 24 weeks, LR+ = 4.01 (95% CI, 2.53-6.34). In women with a history of spontaneous preterm birth (six studies involving 663 women) cervical length at < 20 weeks revealed LR+ = 11.30 (95% CI, 3.59-35.57) and at 20-24 weeks LR+ = 2.86 (95% CI, 2.12-3.87), but there were limited data on the use of cervical length of more than 24 weeks in this group (one study involving 42 women). In women who had had excisional cervical procedures, two studies presented data on cervical length (one at < 24 weeks and one at > 24 weeks), finding cervical length at < 24 weeks to be predictive of spontaneous preterm birth at < 35 weeks (LR+ = 2.91, 95% CI, 1.69-5.01). One study (of 64 women) evaluated cervical length in women with uterine anomalies, finding it predictive of spontaneous preterm birth at < 35 weeks (LR+ = 8.14, 95% CI, 3.12-21.25).

CONCLUSION

Cervical length measured by transvaginal ultrasonography in asymptomatic high-risk women predicts spontaneous preterm birth at < 35 weeks. Further research may be warranted to evaluate the use of transvaginal ultrasonography after 24 weeks' gestation in women with a history of spontaneous preterm birth, and in women with uterine anomalies.

Cervical length in women in preterm labor with intact membranes: relationship to intra-amniotic inflammation/microbial invasion, cervical inflammation and preterm delivery

OBJECTIVE

Intra-amniotic infection, diagnosed by microbial invasion of the amniotic cavity (MIAC) and/or the presence of intra-amniotic inflammation (IAI), is related to adverse perinatal outcome in women with preterm labor. Due to the subclinical nature of IAI, a correct diagnosis depends on amniocentesis, which is an invasive method not performed as a clinical routine. The aim of this study was to evaluate if cervical length measured by transvaginal sonography could assist in the identification of women at high risk for IAI.

METHODS

Cervical length was assessed by transvaginal sonography in 87 women with singleton pregnancies in preterm labor (<34 weeks of gestation). Cervical (n=87) and amniotic (n=55) fluids were collected. Polymerase chain reactions for Ureaplasma urealyticum and Mycoplasma hominis, and culture for aerobic and anaerobic bacteria, were performed. Interleukin (IL)-6 and IL-8 were analyzed by enzyme-linked immunosorbent assay.

RESULTS

IAI was present in 25/55 (45%) of the patients presenting with preterm labor who underwent amniocentesis. Women with IAI had a significantly shorter cervical length (median, 10 (range, 0-34) mm) than had those without IAI (median, 21 (range, 11-43) mm) (P<0.0001). Receiver-operating characteristics curve analysis showed that a cervical length (cut-off of 15 mm) predicted IAI (relative risk, 3.6; CI, 1.9-10.0) with a sensitivity of 72%, specificity of 83%, positive predictive value of 78% and negative predictive value of 78%. Cervical length was also significantly associated with preterm birth up to 7 days from sampling and at <or=34 weeks.

CONCLUSION

Cervical length assessed by transvaginal sonography predicts IAI as well as preterm birth and could thereby be a useful clinical tool in the management of patients in preterm labor.

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.