Preterm Labor: Likelihood Ratios

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 likelihood ratios of findings for Preterm Labor are listed below. See the left navigation bar to change the display.

Good Positive and Negative Likelihood Ratios

Finding	+LR	-LR	Comments, Study
Cervical Length Plus fFN Duplicate	8.6	0.2	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
Cervical Length Plus fFN Duplicate	3.5	0.4	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
Cervical Length	2	0.4	cervical length <=25mm for delivery <35 wk Study: Am J Obstet Gynecol. 2006 Jan;194(1):138-43. PMID 16389023
Fetal Fibronectin	3.3	0.5	>=50ng/ml, for delivery <35 wk Study: Am J Obstet Gynecol. 2006 Jan;194(1):138-43. PMID 16389023