Intended for healthcare professionals

Clinical Review ABC of preterm birth

Obstetric issues in preterm birth

BMJ 2004; 329 doi: (Published 30 September 2004) Cite this as: BMJ 2004;329:783
  1. Deirdre J Murphy,
  2. Peter W Fowlie,
  3. William McGuire


    Predicting and preventing preterm labour and choosing the safest method of delivery are important challenges in reducing the number of preterm births and improving outcomes for mother and baby. This article covers the predictive tests, methods of prevention, maternal and fetal indications for preterm birth, and various approaches to delivery.

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    Length of the endocervix can be measured using transvaginal sonography


    Most preterm deliveries follow spontaneous onset of preterm labour or preterm prelabour rupture of the amniotic membranes (pPROM). Much work has been done (with limited success) to find diagnostic tests that predict accurately if a woman who is at risk of preterm delivery will go on to deliver preterm. For these women, who may have a history of preterm birth or clinical signs of preterm labour, such tests would allow early and targeted use of antenatal interventions. These interventions, especially antenatal corticosteroids, improve neonatal and long term outcomes for preterm infants.

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    Antenatal corticosteroids

    The most common clinical tests used to determine the risk of preterm labour are transvaginal sonography (to measure the length of the endocervix) and the cervicovaginal fetal fibronectin test. These tests have high negative predictive values—that is, if results are negative then the women probably will not progress to preterm delivery. Although there does not seem to be a role for routine use of the fibronectin test or transvaginal sonography to screen women for preterm birth, women thought to be at high risk can be reassured by negative results. This may help women to avoid unnecessary interventions such as antenatal transfer to a distant perinatal unit.

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    Cervicovaginal fetal fibronectin test


    Current medical approaches to preventing preterm labour include the use of tocolytic drugs, antibiotic treatment, and cervical cerclage.

    Tocolytic drugs

    Tocolytic drugs can delay the progress of preterm labour in the short term but maternal side effects include hypotension, …

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