Preterm Labor: Sensitivity and Specificity

Introduction: Generally defined as birth <37 weeks. See also tests to determine Risk of Preterm Labor. The patients here are symptomatic with labor.

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Prevalence

Population / Calculator	Prevalence	Comments / Study / Link
women hospitalized for preterm labor between 18 and 34 completed weeks' gestation	13.4%	for delivery <35wk Am J Obstet Gynecol. 2006 Jan;194(1):138-43. PMID 16389023
Women with preterm labor	17.1%	for delivery within 28 days Acta Obstet Gynecol Scand. 2002 Jan;81(1):58-63. PMID 11942889
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The sensitivity and specificity of findings for Preterm Labor are listed below. See the left navigation bar to change the display.

Pre-Test Probability (Prevalence): %.	Post-Test Probability (Predictive Value): %.	Switch to display mode.
Note that calculating probabilities from more than one** finding is inherently inaccurate because findings are not independent. (For example, using two positive findings that share a common pathogenesis is likely to overestimate the true probability.)

Sensitive and Specific Findings
Finding	Result	Sensitivity	Specificity
[ + ] Cervical Length Plus fFN	+ 0 -	86%	90%
cervical length <=20mm OR length 21-31mm + positive fFN for delivery within 28 days Study: Acta Obstet Gynecol Scand. 2002 Jan;81(1):58-63. PMID 11942889

Poorly Diagnostic Findings
Finding	Result	Sensitivity	Specificity
[ + ] Cervical Length Plus fFN	+ 0 -	67%	81%
cervical length <=15mm OR cervical length 16-30mm + fFN >=50ng/ml for delivery <35wk in this study, results not significantly different from using fetal fibronectin alone (but saves fFN tests) Study: Am J Obstet Gynecol. 2006 Jan;194(1):138-43. PMID 16389023
[ + ] Fetal Fibronectin	+ 0 -	63%	81%
>=50ng/ml, for delivery <35 wk Study: Am J Obstet Gynecol. 2006 Jan;194(1):138-43. PMID 16389023
[ + ] Cervical Length	+ 0 -	75%	63%
cervical length <=25mm for delivery <35 wk Study: Am J Obstet Gynecol. 2006 Jan;194(1):138-43. PMID 16389023