The epidemiology of preterm labour--why have advances not equated to reduced incidence?
ABSTRACT The major burden of preterm birth is in the developing world, where most of the increasing death and morbidity is secondary to infectious diseases such as malaria, HIV, tuberculosis, bacterial vaginosis and intestinal parasites. In some developing countries, the growth of medical care has outstripped the growth of preventive public health, with an associated increase in iatrogenic preterm births. In developed countries, more than one-third of preterm births are medically indicated because of conditions such as fulminating pre-eclampsia or severe intrauterine growth restriction. Neither of these conditions is currently preventable. One in five preterm births is associated with multiple pregnancy, and these have been greatly increased by assisted reproduction techniques. The use of tocolytics has proved disappointing perhaps because inflammation rather than spontaneous uterine activity is increasingly recognised as the final common pathway. Inappropriate antibiotics used late in pregnancy are ineffective and may have adverse effects. Currently, the most promising interventions are public health related and include reducing the transmission of communicable diseases, improvements in the management of diabetes and reduction in harmful behaviours such as smoking and drug abuse.
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ABSTRACT: Recent studies suggest that periodontal disease, as a source of subclinical and persistent infection, may induce systemic inflammatory responses that increase the risk of adverse pregnancy outcomes. To examine the existing evidence on the relationship between periodontal disease and adverse pregnancy outcomes. Published studies identified via searches of the MEDLINE, EMBASE, CINAHL, and Current Contents full-text databases. We identified and selected observational studies (i.e. case-control, cross-sectional, and cohort) and nonrandomised controlled studies or randomised controlled trials that examined periodontal disease as a risk factor for adverse pregnancy outcomes. Odds ratios (OR) or risk ratios (RR) were extracted or calculated from the studies' data. We calculated pooled effect size for two clinical controlled trials but not for the observational studies due to the heterogeneity in definitions for periodontal disease and adverse pregnancy outcomes across studies. Twenty-five studies (13 case-control, 9 cohort, and 3 controlled trials) were identified. The studies focused on preterm low birthweight, low birthweight, preterm birth, birthweight by gestational age, miscarriage or pregnancy loss, and pre-eclampsia. Of the chosen studies, 18 suggested an association between periodontal disease and increased risk of adverse pregnancy outcome (ORs ranging from 1.10 to 20.0) and 7 found no evidence of an association (ORs ranging from 0.78 to 2.54). Three clinical trial studies suggest that oral prophylaxis and periodontal treatment can lead to a 57% reduction in preterm low birthweight (pooled RR 0.43; 95% CI 0.24-0.78) and a 50% reduction in preterm births (RR 0.5; 95% CI 0.20-1.30). Periodontal disease may be associated with an increased risk of adverse pregnancy outcome. However, more methodologically rigorous studies are needed for confirmation.BJOG An International Journal of Obstetrics & Gynaecology 03/2006; 113(2):135-43. · 3.76 Impact Factor
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ABSTRACT: Socio-economic disadvantage is usually associated with low birthweight (LBW). However, it has been shown that Mexican Americans, despite being economically less advantaged, present LBW rates that are similar to or lower than those found among white women in the US. This fact has been called 'the epidemiological paradox of low birthweight'. Natality data from Brazil revealed the existence of a similar paradox: LBW rates are higher in more developed than in less developed regions within the country. In this study, data from two population-based cohort studies carried out in the nineties, including 2439 births in Sao Luis, a poor city in north-eastern Brazil, and 2839 births in Ribeirao Preto, a socio-economically well-off city in south-eastern Brazil, were used to explore this paradox. The method proposed by Wilcox and Russell and a graphic analysis of the frequency distribution of birthweight according to gestational age were used to provide indirect information about possible gestational age misclassification. Contrary to expectations, the LBW rate was higher in Ribeirao Preto than in Sao Luis (10.7 vs. 7.6%, P <0.001), while preterm birth (PTB) rate (12.7 vs. 12.1%, P=0.520) and percentage of small-for-gestational-age (SGA) infants (12.5 vs. 13.5%, P=0.290) were similar for the two cities. However, SGA rate among preterm infants was higher in Ribeirao Preto (16.4 vs. 9.8%, P=0.014). A bimodal distribution of birthweight was observed for children with less than 32 weeks in Sao Luis. As estimated by the Wilcox and Russell method, the residual distribution was greater in Ribeirao Preto than in Sao Luis (3.4 vs. 2.4%). Part of the LBW paradox observed for the two cities was due to the higher PTB rate and higher number of preterm SGA infants in Ribeirao Preto. Factors such as greater medical intervention in preterm newborns close to the end of pregnancy in more developed municipalities, artefacts in the determination of gestational age, and the under-registration of livebirths and registration of livebirths as stillbirths in less developed municipalities may explain why LBW rates in Brazil are higher in richer than in poorer municipalities.Paediatric and Perinatal Epidemiology 02/2005; 19(1):43-9. · 2.16 Impact Factor
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ABSTRACT: To determine whether metronidazole reduces early preterm labour in asymptomatic women with positive vaginal fetal fibronectin (fFN) in the second trimester of pregnancy. Randomised placebo-controlled trial. Fourteen UK hospitals (three teaching). Pregnancies with at least one previous risk factor, including mid-trimester loss or preterm delivery, uterine abnormality, cervical surgery or cerclage. Nine hundred pregnancies were screened for fFN at 24 and 27 weeks of gestation. Positive cases were randomised to a week's course of oral metronidazole or placebo. Primary outcome was delivery before 30 weeks of gestation. Secondary outcomes included delivery before 37 weeks. The Trial Steering Committee (TSC) recommended the study be stopped early; 21% of women receiving metronidazole (11/53) delivered before 30 weeks compared with 11% (5/46) taking placebo [risk ratio 1.9, 95% confidence interval (CI) 0.72-5.09, P = 0.18]. There were significantly more preterm deliveries (before 37 weeks) in women treated with metronidazole 33/53 (62%) versus placebo 18/46 (39%), risk ratio 1.6, 95% CI 1.05-2.4. fFN was a good predictor of early preterm birth in these asymptomatic women; positive and negative predictive values (24 weeks of gestation) for delivery by 30 weeks were 26% and 99%, respectively (positive and negative likelihood ratios 15, 0.35). Metronidazole does not reduce early preterm birth in high risk pregnant women selected by history and a positive vaginal fFN test. Preterm delivery may be increased by metronidazole therapy.BJOG An International Journal of Obstetrics & Gynaecology 02/2006; 113(1):65-74. · 3.76 Impact Factor