Diagnosis of preterm labor
- Charles J Lockwood, MD, MHCM
Charles J Lockwood, MD, MHCM
- Section Editor — Obstetrics
- Senior Vice President, USF Health
- Dean, Morsani College of Medicine
- Professor, Obstetrics and Gynecology
- University of South Florida
Identifying women with preterm contractions who will actually deliver preterm is an inexact process, even though preterm labor is one of the most common reasons for hospitalization of pregnant women. Accurate identification of women truly in preterm labor allows appropriate application of interventions that can improve neonatal outcome: antenatal corticosteroid therapy, group B streptococcal infection prophylaxis, magnesium sulfate for neuroprotection, and transfer to a facility with an appropriate level nursery (if necessary). On the other hand, accurate triage of women not actually in preterm labor can avoid performance of unnecessary interventions and associated costs for the approximately 50 percent of patients with suspected preterm labor who will go on to deliver at term without tocolytic therapy .
This topic will describe our approach to the diagnostic evaluation of women who present with possible preterm labor and provide an overview of issues related to preterm birth. Treatment of preterm labor is discussed separately. (See "Inhibition of acute preterm labor".)
Pathogenesis — The pathophysiology of preterm labor involves at least four primary pathogenic processes that result in a final common pathway ending in spontaneous preterm labor and delivery:
●Activation of the maternal or fetal hypothalamic-pituitary-adrenal axis associated with either maternal anxiety and depression or fetal stress
●Inflammation and infection
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- PRETERM LABOR
- Clinical findings
- Diagnostic evaluation
- - History and initial examinations
- - Speculum examination
- - Digital cervical examination
- - Transvaginal ultrasound examination
- - Obstetrical ultrasound examination
- - Laboratory evaluation
- Fetal fibronectin for selected patients
- - Qualitative fFN
- - Quantitative fFN
- Other laboratory tests
- Triage singleton pregnancies
- - ≥34 weeks of gestation
- - <34 weeks of gestation
- Ultrasound ± fetal fibronectin examination
- - Cervical length 20 to <30 mm
- - Cervical length <20 mm
- - Cervical length ≥30 mm
- Triage twin pregnancies
- - ≥34 weeks of gestation
- - <34 weeks of gestation
- Treatment of women <34 weeks with suspected preterm labor
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS
- Preterm labor