Obstet Gynecol Sci.  2017 Jul;60(4):329-335. 10.5468/ogs.2017.60.4.329.

Second trimester cervical length measurement for prediction spontaneous preterm birth in an unselected risk population

• Peixoto AB
• da Cunha Caldas TMR
• Tahan LA
• Petrini CG
• Martins WP
• Costa FD
• Araujo Júnior E

• KMID: 2386273
• DOI: http://doi.org/10.5468/ogs.2017.60.4.329

Abstract

OBJECTIVE
To assess the predictive capacity of cervical length (CL) measurement underwent during the second trimester ultrasound for prediction preterm birth <32, 34, and 37 weeks of gestation in an unselected risk population.
METHODS
A retrospective cohort study was performed with 751 singleton pregnancies between 20 and 24+6 weeks of gestation. The CL measurement (mm) using the transvaginal route was obtained in a sagittal view and the calipers positioned to measure the linear distance between the triangular area of echodensity at the external os and the internal os. To compare the preterm (<37 weeks) and term births (≥37 weeks), we used unpaired t test. We assessed whether the CL measurement was dependent of gestational age by performing a linear regression and assessing the coefficient of determination (R²). We additionally assessed the accuracy of CL measurement to predict preterm birth by assessing the area under receiver operating characteristics curves with its respective confidence intervals (CIs) 95%.
RESULTS
Preterm birth <37 weeks was found in 13.6% (102/751) of pregnant women. Short cervix (≤25 mm) was found in 2.7% (20/751) of pregnancies. Only 30% (6/20) of pregnant women with short cervix have used progesterone to prevent preterm birth. There was a weak correlation between CL measurement and gestational age at delivery (R²=0.01, P=0.002). Receiver operating characteristics curve analysis of the ability of CL measurement to predict preterm birth <32, 34, and 37 weeks, showed an area under the curve of 0.693 (95% CI, 0.512 to 0.874), 0.472 (95% CI, 0.353 to 0.591), 0.490 (95% CI, 0.426 to 0.555), respectively.
CONCLUSION
There was a weak correlation between CL measurement and gestational age at delivery. In an unselected population, CL measurement screening at 20 to 24+6 weeks of gestation does not seem to be a good predictor of preterm birth.

Keyword

Cervix uteri; Pregnancy trimester, second; Preterm birth; Screening; Transvaginal ultrasound

MeSH Terms

Cervical Length Measurement*
Cervix Uteri
Cohort Studies
Female
Gestational Age
Humans
Linear Models
Mass Screening
Pregnancy
Pregnancy Trimester, Second*
Pregnant Women
Premature Birth*
Progesterone
Retrospective Studies
ROC Curve
Term Birth
Ultrasonography
Progesterone

Figure

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  Fig. 1 Transvaginal ultrasound examination showing the cervical length measurement at 22 weeks of gestation. (A) Normal cervical length measurement and (B) short cervix with funneling.

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  Fig. 2 Scatter plot of the correlation between cervical length measurement (mm) and gestational age (weeks) at delivery.

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  Fig. 3 Receiver operating characteristics curves to display the cervical length measurement ability to predict preterm birth (A) <32, (B) 34, and (C) 37 weeks of gestation. Diagonal segments are produced by ties.

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