Sonographic measurement of cervical length and risk of preterm delivery

Antenatal corticosteroids-to-birth interval in preterm birth

Objectives: The purpose of this study was to compare short-term outcomes in children born between 24 and 34 weeks' gestation, according to observed antenatal corticosteroids (ACS)-to-birth intervals. Research question: 'Is there a difference in short-term outcomes between observed ACS-to-birth intervals across a range of gestational ages at birth?'Methods: Cohort study assessing differences in incidence of short-term neonatal outcomes according to the observed interval between the last administration of ACS and birth. Linear, non-weighted GEE models with an independence working correlation structure were fitted to infant level data providing valid point estimates for either incidence or rate differences (binary outcomes) or average differences (continuous outcomes).Results: Of 886 children, 35.9% were born within 2 days after the last administration of ACS, 32.2% within 2 to 7 days, 14.1% within 8 to 14 days, and 17.8% more than 14 days after. Across gestational ages at birth, there were no differences in birth weight between children born at an ACS-to-birth interval of 7 days or less compared to more than 7 days, nor were there differences in respiratory outcomes, cerebral outcomes, or composite outcome.Conclusion: Drawing conclusions on the importance of the ACS-to-birth interval is difficult due to the post-hoc nature of the variable. In the absence of tools to better estimate if and when PTB will occur, it might not have any value in daily practice, regardless of whether there is an optimal ACS-to-birth interval or not.

Reference range of the weekly uterine cervical length at 8 to 38 weeks of gestation in the center of Iran

BACKGROUND

There is an inverse relation between the uterine cervical length during pregnancy and the frequency of preterm delivery. The purpose of this study was to construct a chart and evaluate the cervical length at 8 to 38 weeks of normal gestation in the center of Iran.

MATERIALS AND METHODS

Uterine cervical length was measured on 930 asymptomatic pregnant women by abdominal ultrasonographic technique. For statistical evaluation, regression analysis and calculation of percentiles were performed.

RESULTS

Our data show a significant decrease in uterine cervical length with increasing gestational age. The mean uterine cervical length exhibits minimal changes from 10 to 24 weeks for most women in this study, although the shortening is more prominent at 33 to 38 weeks' gestation. The mean shortening of the uterine cervical length between the second and the ninth months was 14.82% (P < 0.05). Also, the cervical length means in trimesters 1, 2 and 3 were 39.30 ± 4.33, 38.28 ± 5.13 and 36.58 ± 4.58 mm, respectively. The third trimester showed a significant reduction (P < 0.05) in cervical length compared to the first and second trimesters (6.92% and 4.44%, respectively). New charts with the 5(th), 10(th), 50(th), 90(th), and 95(th) percentile are presented.

CONCLUSION

Our study provides a new chart and reference values for normal uterine cervical length throughout gestation based on a large sample in the center of Iran. There was a progressive decrease in mean uterine cervical length with increasing gestational age in the population of this study. Our established charts for uterine cervical length throughout gestation might be more useful than a single cut-off value for more efficient prevention and management of preterm birth.

Predictive factors for latency period in viable pregnancies complicated by preterm premature rupture of the membranes

Objective:

In this study, we aimed to evaluate some laboratory and clinical factors in the prediction of latency period for pregnant patients complicated with preterm premature rupture of the membranes.

Materials and Methods:

Sixty-five pregnant patients between 24 and 34 weeks of gestation, who were admitted to University of Çukurova School of Medicine Hospital with the diagnosis of preterm premature rupture of the membranes (PPROM) between January 01, 2013 and December 31, 2013, were included in this study. Serum CRP, procalcitonin, sedimentation rate, leukocyte count and cervical length (measured with transvaginal ultrasound) of patients were analyzed for the correlation with the latency period.

Results:

None of the parameters were found to be correlated with the latency period. However, patients with cervical length of <25 mm were found to have shorter duration of latency.

Conclusion:

Although preterm premature rupture of the membranes is thought to be either an infection-based disease or a disease increasing the risk of infectious complications, major infection markers are not found to be helpful criteria for the prediction of latency period. Patients with a cervical length of <25 mm can be expected to deliver earlier and, therefore, can be referred to a tertiary center earlier.

Is cervical length associated with maternal characteristics?

OBJECTIVE

Women with a mid-trimester short cervical length (CL) are at increased risk for preterm delivery. Consequently, CL measurement is a potential screening tool to identify women at risk for preterm birth. Our objective was to assess possible associations between CL and maternal characteristics.

STUDY DESIGN

A nationwide screening study was performed in which CL was measured during the standard anomaly scan among low risk women with a singleton pregnancy. Data on maternal height, pre-pregnancy weight, ethnicity, parity and gestational age at the time of the CL measurement were collected from January 2010 to December 2012. Univariable and multivariable linear regression analyses were performed to assess the relationship between CL and maternal characteristics.

RESULTS

We included 5092 women. The mean CL was 44.3mm. No association was found between CL and maternal height or gestational age of the measurement. Maternal weight was associated with CL (p=0.007, adjusted R(2) 0.03). Separate analysis for BMI did not change these results. Ethnicity, known in 2702 out of 5092 women, was associated with CL (mean CL in Caucasian women 45.0mm, Asian 43.9mm, Mediterranean 43.1mm, and African 41.8mm, p=0.003), as well as parity (mean CL multiparous 45.3mm, nulliparous 43.5mm, p<0.0001).

CONCLUSION

Shorter mid-trimester cervical length is associated with higher maternal weight, younger maternal age, nulliparity and non-Caucasian ethnicity, but not with maternal height.

The clinical utility of sonographic cervical length in the management of preterm parturition at 28-32 weeks of gestation

OBJECTIVES

The aim of this study was to evaluate the role of cervical length measurement in early third trimester (28-32 weeks) as a predictor of preterm delivery (PTD), in women presenting with preterm parturition.

METHODS

Cervical length was measured prospectively, in singleton pregnancies at 28-32 weeks with preterm contractions (PTC). A multivariate linear regression model was performed to assess the association between cervical length and gestational age at delivery. Logistic regression analysis with PTD before 34 and 37 weeks of gestation as the outcome variable was performed to control for confounders.

RESULTS

Fifty-six women were included, mean gestational week at presentation and at delivery were 29.88 ± 1.13 and 37.05 ± 2.86, respectively. There was a direct association between short cervical length at admission and gestational week at delivery (p = 0.027). This association remained significant even after controlling for confounders. Short cervical length was significantly associated with PTD before 34 (p = 0.045) or 37 (p = 0.046) weeks of gestation.

CONCLUSIONS

Third trimester cervical length measurement in patients with PTC is associated with gestational week at delivery, as well as PTD prior to 34 and 37 weeks of gestation. Therefore, examining cervical length is clinically valuable and probably cost-effective during early third trimester.

Predictive value of cervical length in women with threatened preterm labor

OBJECTIVE

To assess the predictive role of ultrasonographic cervical length for preterm delivery in women with threatened preterm labor.

METHODS

A retrospective cohort study of women with singleton pregnancies who presented with preterm labor before 34 weeks of gestation and underwent ultrasonographic measurement of cervical length in a tertiary medical center. Women with cervical cerclage, cervical dilatation greater than 3 cm at presentation, and pregnancies complicated by placental abruption, clinical chorioamnionitis, stillbirth, or major fetal anomalies were excluded. The predictive accuracy of cervical length for preterm delivery was analyzed using both fixed thresholds and outcome-specific thresholds, which are associated with a detection rate of 90%, false-positive rate of 10%, or the inflexion point of the receiver operator characteristic curve.

RESULTS

Between 2007 and 2012, 1,077 women presented with preterm labor and met the study criteria. The correlation between cervical length and the time interval to delivery was significant but weak (r=0.293, P<.001). Cervical length was independently associated with the risk of preterm delivery at less than 37, 35, and 32 weeks of gestation and within 14 and 7 days from presentation (a 4-7% decrease in the risk for each additional millimeter of cervical length) as well as with the time interval between presentation and delivery (each additional 2 mm was associated with an increase of 1 day). Overall, the accuracy of cervical length in predicting preterm delivery was relatively poor.

CONCLUSION

Although cervical length is an independent predictor of preterm delivery in women with preterm labor, its predictive accuracy as a single measure is relatively limited.

LEVEL OF EVIDENCE

: II.

The short-term prediction of preterm birth: a systematic review and diagnostic metaanalysis

OBJECTIVE

To assess the diagnostic accuracy of fetal fibronectin (fFN), fetal breathing movements (FBM), and cervical length (CL) for the short-term prediction of preterm birth in symptomatic patients.

STUDY DESIGN

Diagnostic metaanalysis using bivariate methods.

RESULTS

Pooled sensitivities for fFN, FBM, and CL for delivery within 48 hours of testing were 0.62 (95% confidence interval [CI], 0.43-0.78), 0.75 (95% CI, 0.57-0.87) and 0.77 (95% CI, 0.54-0.90), respectively. Pooled specificities for fFN, FBM, and CL for delivery within 48 hours were 0.81 (95% CI, 0.74-0.86), 0.93 (95% CI, 0.75-0.98) and 0.88 (95% CI, 0.84-0.91). Pooled sensitivities for fFN, FBM, and CL for delivery within 7 days were 0.75 (95% CI, 0.69-0.80), 0.67 (95% CI, 0.43-0.84), and 0.74 (95% CI, 0.58-0.85). Pooled specificities for fFN, FBM, and CL for delivery within 7 days were 0.79 (95% CI, 0.76-0.83), 0.98 (95% CI, 0.83-1.00) and 0.89 (95% CI, 0.85-0.92). Based on a pretest probability of 10% for delivery within 48 hours, posttest probabilities (positive and negative) were 27% and 5% for fFN, 54% and 3% for fFN, and 42% and 3% for CL. For a pretest probability of 20% for delivery within 7 days, posttest probabilities (positive and negative) were 48% and 7% for fFN, 89% and 8% for FBM, and 63% and 7% for CL.

CONCLUSION

In symptomatic patients, for fFN, absence of FBM, and CL have diagnostic use as predictors of delivery within 48 hours and within 7 days of testing. Absence of FBM appears to be the best test for predicting preterm birth.