Cervical ultrasonography compared with manual examination as a predictor of preterm delivery,☆☆,

Presented at the Seventeenth Annual Meeting of the Society of Perinatal Obstetricians, Anaheim, California, January 20-25, 1997.
https://doi.org/10.1016/S0002-9378(97)70259-XGet rights and content

Abstract

OBJECTIVE: Our purpose was to compare the accuracy of ultrasonographic and manual cervical examinations for the prediction of preterm delivery.

STUDY DESIGN: One hundred two singleton pregnancies at high risk for preterm delivery were followed up prospectively from 14 to 30 weeks with both serial cervical ultrasonography measurements and manual examinations of the length of the cervix. The primary outcome studied was preterm (<35 weeks) delivery.

RESULTS: Excluding six induced preterm deliveries, 96 pregnancies were analyzed. The mean cervical length measured by ultrasonography was 20.6 mm in pregnancies delivered preterm (n = 17) and 31.3 mm in pregnancies delivered at term (n = 79) (p = 0.003); the mean cervical lengths measured by manual examination were 16.1 mm and 18.6 mm in the same preterm and term pregnancies, respectively (not significant). The sixteenth- and twentieth-week ultrasonographic cervical lengths predicted preterm delivery most accurately (p < 0.0005). The 25th percentiles of ultrasonographic (25 mm) and manual (16 mm) cervical lengths showed relative risks for preterm delivery of 4.8 (95% confidence interval 2.1 to 11.1, p = 0.0004) and 2.0 (95% confidence interval 0.5 to 4.7, p = 0.1), respectively; sensitivity, specificity, and positive and negative predictive values were 59%, 85%, 45%, 91%, and 41%, 77%, 28%, and 86%, respectively.

CONCLUSION: Cervical length measured by ultrasonography is a better predictor of preterm delivery than is cervical length measured by manual examination. Cervical ultrasonography in patients at high risk for preterm birth seems to be most predictive of preterm delivery when it is performed between 14 and 22 weeks' gestation. (Am J Obstet Gynecol 1997;177:723-30.)

Section snippets

Material and methods

The study was performed from June 1993 to March 1996 at two clinical sites. Patients with the following historic criteria indicating an increased risk of preterm delivery were eligible for inclusion: one or more preterm delivery between 14 and 32 weeks' gestation, mullerian anomaly, two or more voluntary terminations, diethylstilbestrol (DES) exposure, cone biopsy, and Ehlers-Danlos syndrome. Women with multiple gestation, placenta previa, prophylactic cerclage, or a major fetal anomaly were

Results

Of 102 pregnancies entered in the study, 6 were excluded because of induced preterm delivery, leaving 96 pregnancies for analysis. Each patient received an average of 5.5 cervical ultrasonographic and 5.6 manual examinations between 14 and 30 weeks. In 17 of 96 (18%) patients delivery occurred before 35 weeks. Thirty of 96 (31%) underwent tocolysis. Demographic characteristics are presented in Table I.

There was no difference in age, race, parity, health care provider, or history of smoking

Comment

We report the first longitudinal study to demonstrate that measurement of the cervix by ultrasonographic examination is a better predictor of preterm delivery than is measurement by manual examination in patients with risk factors for preterm delivery. Cervical assessment by manual examinations has been the traditional method for the prediction of preterm delivery. With use of l cm cervical length as the cutoff value at 27 to 28 weeks or a Bishop score of 4 between 22 weeks and 27 weeks 6 days

Acknowledgements

We thank Sheila Amand, RDMS, Sue Henry, RDMS, Marianne Candelora, RDMS, Jane Owens, RDMS, Pamela L. Hilpert, MD, PhD, and Jane Hirshberg, RNC, BSN, for their contributions and Greg Maislin, MS, MA, for statistical consulting for the logistic regression analysis.

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    From the Divisions of Maternal-Fetal Medicine, Departments of Obstetrics and Gynecology, Jefferson Medical College of Thomas Jefferson Universitya and Pennsylvania Hospital,b and the Perinatology Research Branch, National Institute of Child Health and Human Development.c

    ☆☆

    Reprint requests: Vincenzo Berghella, MD, Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Jefferson Medical College, 834 Chestnut St., Suite 400, Philadelphia, PA 19107.

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