Cervical length as a predictor of preterm delivery: gestational age-related percentiles vs fixed cut-offs.

Department of Gynecology, Obstetrics and Neonatology, University of Parma, Parma, Italy.
Acta bio-medica: Atenei Parmensis 01/2008; 78(3):220-4.
Source: PubMed

ABSTRACT To determine whether preterm delivery is more effectively predicted by sonographic cervical length measurement using fixed cut-off or gestational age-specific percentiles.
One hundred and eight patients hospitalized for suspected preterm labor (PTL) were studied prospectively between the 20th and the 33rd week of gestation.
Cervical length below 15 mm, 25 mm and the 2.5th centile showed substantially equivalent odds ratios for delivery within 7 days (7.5, 7.6, and 7.1, respectively), while for delivery before the 34th week the odds ratios varied between 3.6 with cervical length <2.5rh centile and 6.2 with cervical length <25 mm. Moreover, the negative predictive value for delivery within 7 days exceeded 90% when cervical length was above 25 mm, the 10th and the 2.5th percentile, and 85% when above 15 mm.
The comparison of fixed and gestational age-specific cut-offs demonstrates a better reliability of fixed cut-offs (15 or 25 mm) in predicting preterm delivery, both before 34 weeks and within 7 days of the ultrasound examination.

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