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Preterm labor

Last reviewed: 25 Jun 2024
Last updated: 22 Mar 2024



History and exam

Key diagnostic factors

  • history of preterm labor, cervical trauma, or induced abortion
  • multifetal pregnancy and presence of maternal infection
  • uterine contractions
  • preterm prelabor rupture of membranes (PPROM)
  • advanced cervical dilation
  • cervical length <2 cm
Full details

Other diagnostic factors

  • increased maternal or fetal heart rate
  • nonspecific lower abdominal or back pain
  • fever
  • vaginal bleeding
Full details

Risk factors

  • previous preterm labor
  • previous cervical trauma
  • previous induced abortion
  • maternal infections
  • multifetal pregnancies
  • short cervical length
  • positive fetal fibronectin test
  • preterm prelabor rupture of membranes (PPROM)
  • fetal abnormalities
  • smoking
  • body mass index (BMI) <19 kg/m²
  • social factors and ethnicity
  • fertility treatment
  • polyhydramnios
  • domestic violence
  • poor dental hygiene
  • late-stage cesarean section
Full details

Diagnostic tests

1st tests to order

  • nonstress cardiotocogram
  • tocography
  • transvaginal ultrasound of the cervix
  • cervico-vaginal swab for fetal fibronectin
  • CBC
  • CRP
  • urine dipstick
  • urine microscopy, culture, and sensitivity
  • high vaginal/rectal culture
Full details

Tests to consider

  • microscopy of vaginal fluid
  • Kleihauer blood test
  • urine toxicology screen
  • insulin-like growth factor binding protein-1 (IGFBP-1) test
  • placental alpha microglobulin-1 (PAMG-1)
Full details

Treatment algorithm


threatened preterm labor (TPTL)

preterm prelabor rupture of membranes (PPROM)

high risk of imminent delivery without PPROM



Andrew H. Shennan, MD, FRCOG

Professor of Obstetrics

King's College London




AHS has given talks for Hologic, the manufacturer of fetal fibronectin, and has received funds to his institute for research. AHS is an author of several references cited in this topic.

Joanna C. Girling, MA, MRCP, FRCOG

Consultant in Obstetrics and Gynaecology

West Middlesex University Hospital




JCG declares that she has no competing interests.

Peer reviewers

Jo Trinder, MD

Consultant Obstetrician and Gynaecologist

St Michael's Maternity Wing

Bristol Royal Infirmary




JT has accepted honoraria for speaking to groups of midwives and doctors about miscarriage management.

Kirsty Dundas, MBChB, DCH, FRCOG

Consultant Obstetrician and Gynaecologist

Royal Infirmary of Edinburgh

Honorary Senior Lecturer

University of Edinburgh




KD declares that she has no competing interests.

Deidre Lyell, MD

Assistant Professor of Maternal-Fetal Medicine

Stanford University




DL declares that she has no competing interests.

  • Differentials

    • Placental abruption
    • Urinary tract infection (UTI)
    • Ovarian cyst
    More Differentials
  • Guidelines

    • Guideline no. 430: diagnosis and management of preterm prelabour rupture of membranes
    • Practice bulletin no. 231: multifetal gestations twin, triplet, and higher-order multifetal pregnancies
    More Guidelines
  • Patient information

    Premature labor

    More Patient information
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