Can the optimal cervical length for placing ultrasound-indicated cerclage be identified?
OBJECTIVE
To assess a continuum of cervical length (CL) cut-offs for the efficacy of ultrasound-indicated cerclage in women with previous spontaneous preterm birth (PTB).


METHODS
This was a planned secondary analysis of a multicenter randomized clinical trial of ultrasound-indicated cerclage for the prevention of PTB in high-risk women. The efficacy of cerclage for preventing recurrent PTB < 35, < 32 and < 24 weeks' gestation was assessed using multivariable logistic regression analysis. Odds ratios (ORs) and CIs were estimated for a range of CL cut-offs using bootstrap regression. The 2.5(th) and 97.5(th) percentiles of bootstrapped ORs determined the CIs. Results were illustrated using smoothed curves superimposed on estimated ORs by CL cut-off.


RESULTS
Of 301 women with a CL < 25 mm, 142 underwent ultrasound-indicated cerclage and 159 did not have cerclage placement. The few cases with CL < 10 mm limited the evaluation to CL cut-offs between < 10 mm and < 25 mm. For PTB < 35 weeks, ORs in women with a cerclage and CL < 25 mm were statistically significantly lower than in those without cerclage, and efficacy was maintained at smaller CL cut-offs. Results were similar for PTB < 32 weeks. For PTB < 24 weeks, results differed, with ORs increasing toward unity (no benefit), with wide CIs, for CL cut-offs between < 10 mm and < 15 mm, attributed to the small number of births < 24 weeks.


CONCLUSIONS
The efficacy of ultrasound-indicated cerclage in women with previous spontaneous PTB varies by action point CL cut-off and by PTB gestational age of interest. Cerclage significantly reduces the risk of PTB < 35 and < 32 weeks, at CL cut-offs between < 10 mm and < 25 mm, with the greatest reduction at shorter CL, affirming that women with prior spontaneous PTB and a short CL are appropriate candidates for ultrasound-indicated cerclage. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.
Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL, USA.|Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, AL, USA.
J M
JM
Szychowski
Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, AL, USA.
J
J
Owen
Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, TX, USA.
G
G
Hankins
Department of Obstetrics and Gynecology, The Ohio State University Medical Center, Columbus, OH, USA.
J D
JD
Iams
Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
J S
JS
Sheffield
Department of Obstetrics and Gynecology, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
A
A
Perez-Delboy
Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Thomas Jefferson University, Philadelphia, PA, USA.
V
V
Berghella
Department of Obstetrics and Gynecology, University of California, Irvine, Orange, CA, USA.
D A
DA
Wing
Department of Obstetrics and Gynecology, Saint Peter's University Hospital, New Brunswick, NJ, USA.
E R
ER
Guzman
D000328:Adult; D023802:Cerclage, Cervical; D054791:Cervical Length Measurement; D005260:Female; D005865:Gestational Age; D006801:Humans; D016015:Logistic Models; D011247:Pregnancy; D047928:Premature Birth / Q000000981:diagnostic imaging* / Q000517:prevention & control*; D014481:United States; D002581:Uterine Cervical Incompetence / Q000000981:diagnostic imaging* / Q000601:surgery
cerclage; cervical length; preterm birth prediction; vaginal sonography