Epidemiology and causes of preterm birth

Robert L Goldenberg, Jennifer F Culhane, Jay D Iams, Roberto Romero, Robert L Goldenberg, Jennifer F Culhane, Jay D Iams, Roberto Romero

Abstract

This paper is the first in a three-part series on preterm birth, which is the leading cause of perinatal morbidity and mortality in developed countries. Infants are born preterm at less than 37 weeks' gestational age after: (1) spontaneous labour with intact membranes, (2) preterm premature rupture of the membranes (PPROM), and (3) labour induction or caesarean delivery for maternal or fetal indications. The frequency of preterm births is about 12-13% in the USA and 5-9% in many other developed countries; however, the rate of preterm birth has increased in many locations, predominantly because of increasing indicated preterm births and preterm delivery of artificially conceived multiple pregnancies. Common reasons for indicated preterm births include pre-eclampsia or eclampsia, and intrauterine growth restriction. Births that follow spontaneous preterm labour and PPROM-together called spontaneous preterm births-are regarded as a syndrome resulting from multiple causes, including infection or inflammation, vascular disease, and uterine overdistension. Risk factors for spontaneous preterm births include a previous preterm birth, black race, periodontal disease, and low maternal body-mass index. A short cervical length and a raised cervical-vaginal fetal fibronectin concentration are the strongest predictors of spontaneous preterm birth.

Figures

Figure 1
Figure 1
Percentage of all births classified as preterm in the USA, 1981–2004 Source: Martin JA, Kochanek KD, Strobino DM, Guyer B, MacDorman MF. Annual summary of vital statistics—2003. Pediatrics 2005; 115: 619–34.
Figure 2
Figure 2
Obstetric precursors of preterm birth
Figure 3
Figure 3
Temporal changes in singleton preterm births overall and temporal changes resulting from ruptured membranes, medically indicated preterm labour, and spontaneous preterm labour in USA, 1989–2000 A) Rates in each group by year. B) The percentage change in rates relative to 1989. Figure adapted from reference 9.
Figure 4
Figure 4
Comparison of spontaneous and indicated preterm birth by maternal body-mass index (BMI) Figure adapted from reference 35.
Figure 5
Figure 5
Potential routes of intrauterine infection

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