Brazilian Multicentre Study on Preterm Birth (EMIP): Prevalence and Factors Associated with Spontaneous Preterm Birth

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Abstract

Background

Preterm birth rate is increasing and is currently a worldwide concern. The purpose of this study was to estimate the prevalence of preterm birth in a sample of health facilities in Brazil and to identify the main risk factors associated with spontaneous preterm births.

Methods and Findings

This was a multicentre cross sectional study on preterm births in 20 referral obstetric hospitals with a case-control component to identify factors associated with spontaneous preterm birth. Surveillance was implemented at all centres to identify preterm births. For eligible consenting women, data were collected through a post-delivery questionnaire completed with information from all mother-newborn medical records until death or discharge or at a maximum of 60 days post-delivery, whichever came first. The risk of spontaneous preterm birth was estimated with OR and 95%CI for several predictors. A non-conditional logistic regression analysis was then performed to identify independently associated factors. The overall prevalence of preterm birth was 12.3%. Among them, 64.6% were spontaneous and 35.4% therapeutic. In the case-control component, 2,682 spontaneous preterm births were compared to a sample of 1,146 term births. Multivariate analyses identified the following as risk factors for spontaneous preterm birth among women with at least one previous birth: a previous preterm birth (OR _adj = 3.19, 2.30–4.43), multiple pregnancy (OR _adj = 29.06, 8.43–100.2), cervical insufficiency (OR _adj = 2.93, 1.07–8.05), foetal malformation (OR _adj = 2.63, 1.43–4.85), polyhydramnios (OR _adj = 2.30, 1.17–4.54), vaginal bleeding (OR _adj = 2.16, 1.50–3.11), and previous abortion (OR _adj = 1.39, 1.08–1.78). High BMI (OR _adj = 0.94, 0.91–0.97) and weight gain during gestation (OR _adj = 0.92, 0.89–0.95) were found to be protective factors.

Conclusions

The preterm birth rate in these health facilities in Brazil is high and spontaneous preterm births account for two thirds of them. A better understanding of the factors associated with spontaneous preterm birth is of utmost importance for planning effective measures to reduce the burden of its increasing rates.

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Most cited references 20

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Overweight and obesity in mothers and risk of preterm birth and low birth weight infants: systematic review and meta-analyses

Sarah McDonald, Zhen-Hai Han, Sohail M. Mulla … (2010)

Objective To determine the relation between overweight and obesity in mothers and preterm birth and low birth weight in singleton pregnancies in developed and developing countries. Design Systematic review and meta-analyses. Data sources Medline and Embase from their inceptions, and reference lists of identified articles. Study selection Studies including a reference group of women with normal body mass index that assessed the effect of overweight and obesity on two primary outcomes: preterm birth (before 37 weeks) and low birth weight (<2500 g). Data extraction Two assessors independently reviewed titles, abstracts, and full articles, extracted data using a piloted data collection form, and assessed quality. Data synthesis 84 studies (64 cohort and 20 case-control) were included, totalling 1 095 834 women. Although the overall risk of preterm birth was similar in overweight and obese women and women of normal weight, the risk of induced preterm birth was increased in overweight and obese women (relative risk 1.30, 95% confidence interval 1.23 to 1.37). Although overall the risk of having an infant of low birth weight was decreased in overweight and obese women (0.84, 0.75 to 0.95), the decrease was greater in developing countries than in developed countries (0.58, 0.47 to 0.71 v 0.90, 0.79 to 1.01). After accounting for publication bias, the apparent protective effect of overweight and obesity on low birth weight disappeared with the addition of imputed “missing” studies (0.95, 0.85 to 1.07), whereas the risk of preterm birth appeared significantly higher in overweight and obese women (1.24, 1.13 to 1.37). Conclusions Overweight and obese women have increased risks of preterm birth and induced preterm birth and, after accounting for publication bias, appeared to have increased risks of preterm birth overall. The beneficial effects of maternal overweight and obesity on low birth weight were greater in developing countries and disappeared after accounting for publication bias.

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Births: final data for 2009.

S. Ventura, Ian Mathews, Sharon Kirmeyer … (2011)

This report presents 2009 data on U.S. births according to a wide variety of characteristics. Data are presented for maternal characteristics including age, live-birth order, race and Hispanic origin, marital status, hypertension during pregnancy, attendant at birth, method of delivery, and infant characteristics (period of gestation, birthweight, and plurality). Birth and fertility rates by age, live-birth order, race and Hispanic origin, and marital status also are presented. Selected data by mother's state of residence are shown, as well as birth rates by age and race of father. Trends in fertility patterns and maternal and infant characteristics are described and interpreted. Descriptive tabulations of data reported on the birth certificates of the 4.13 million births that occurred in 2009 are presented. Denominators for population-based rates are postcensal estimates derived from the U.S. 2000 census. The number of births declined to 4,130,665 in 2009, 3 percent less than in 2008. The general fertility rate declined 3 percent to 66.7 per 1,000 women aged 15-44 years. The teenage birth rate fell 6 percent to 39.1 per 1,000. Birth rates for women in each 5-year age group from 20 through 39 years declined, but the rate for women 40-44 years continued to rise. The total fertility rate (estimated number of births over a woman's lifetime) was down 4 percent to 2,007.0 per 1,000 women. The number and rate of births to unmarried women declined, whereas the percentage of nonmarital births increased slightly to 41.0. The cesarean delivery rate rose again, to 32.9 percent. The preterm birth rate declined to 12.18 percent; the low birthweight rate was stable at 8.16 percent. The twin birth rate increased to 33.2 per 1,000; the triplet and higher-order multiple birth rate rose 4 percent to 153.5 per 100,000.

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Spontaneous preterm birth, a clinical dilemma: etiologic, pathophysiologic and genetic heterogeneities and racial disparity.

Ramkumar Menon (2007)

Preterm labor leading to preterm delivery (<37 weeks' gestation) affects approximately 5-7% of live births in developed countries, but significantly higher in developing countries. Prematurity due to preterm birth (PTB) accounts for around 28% of neonatal mortality worldwide. Approximately 45-50% of PTBs are idiopathic or spontaneous, 30% are related to preterm rupture of membranes, and another 15-20% are attributed to medically indicated or elective preterm deliveries. The rate of spontaneous PTB is also increasing and the exact cause is still unclear. Generalized approaches in screening for high risk status of preterm labor and interventions have failed to reduce PTB rates. PTB presents a clinical dilemma due to etiologic, pathophysiologic and genetic heterogeneities. Racial disparity in PTB rates observed in the US further complicates its understanding. PTB is a complex phenotype and is not initiated by a single etiologic agent. Etiologic factors operate through multiple pathophysiologic pathways, and these pathways include highly overlapping biomarkers and molecular factors creating pathophysiologic heterogeneities. In this article, the current understanding of PTB pathophysiology is reviewed and the need for a much broader approach in research, analysis and interpretation of data is explained, where environmental and race/ethnicity specific risk factors may dictate specific pathways leading to PTB. Recent data on amniotic fluid biomarkers and maternal and fetal genetic variants, which indicate huge disparity between races in the US, are also reviewed. These data suggest that gene-gene interactions and gene-environmental interactions produce distinct pathophysiologic pathways with respect to an individual's genetic make-up and environmental risk exposure. Current strategies of high risk screening and intervention measures may not be generalized, and a more individualized approach may be required to understand PTB and its prevention.

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Author and article information

Contributors

Monica da Silva Nunes: Role: Editor

Journal

Journal ID (nlm-ta): PLoS One

Journal ID (iso-abbrev): PLoS ONE

Journal ID (publisher-id): plos

Journal ID (pmc): plosone

Title: PLoS ONE

Publisher: Public Library of Science (San Francisco, USA )

ISSN (Electronic): 1932-6203

Publication date Collection: 2014

Publication date (Electronic): 9 October 2014

Volume: 9

Issue: 10

Electronic Location Identifier: e109069

Affiliations

[1 ]Department of Obstetrics and Gynaecology, School of Medical Sciences, University of Campinas, Campinas, Brazil

[2 ]Centre for Studies in Reproductive Health of Campinas (CEMICAMP), Campinas, Brazil

[3 ]Jundiai School of Medicine, Jundiaí, Brazil

Universidade Federal do Acre (Federal University of Acre), Brazil

Author notes

* E-mail: passini@ 123456caism.unicamp.br

Competing Interests: The authors have declared that no competing interests exist.

Conceived and designed the experiments: RPJ JGC GJL RPT MLN TZD SMH PMR MHS. Performed the experiments: RPJ JGC GJL RPT MLN TZD SMH PMR MHS. Analyzed the data: RPJ JGC GJL RPT MLN TZD SMH PMR RCP MLC MHS. Contributed reagents/materials/analysis tools: RPJ JGC GJL RPT MLN TZD SMH MHS. Wrote the paper: RPJ JGC GJL RPT MLN TZD SMH PMR RCP MLC MHS.

¶ Membership of the Brazilian Multicentre Study on Preterm Birth study group is provided in the Acknowledgments.

Article

Publisher ID: PONE-D-14-04383

DOI: 10.1371/journal.pone.0109069

PMC ID: 4192080

PubMed ID: 25299699

SO-VID: 33e3a7d3-8e77-4925-ae51-0df2bde04a28

License:

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

History

Date received : 3 February 2014

Date accepted : 8 September 2014

Page count

Pages: 12

Funding

The authors thank the CNPq (Brazilian National Research Council) and Fapesp (Foundation for Support to Research of the State of Sao Paulo) for the financial sponsorship of this study, Process Fapesp 2009/53245-5 (Call AP.PPSUS-1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Brazilian Multicentre Study on Preterm Birth (EMIP): Prevalence and Factors Associated with Spontaneous Preterm Birth

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Abstract

Background

Methods and Findings

Conclusions

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PLOS Climate

Most cited references 20

Overweight and obesity in mothers and risk of preterm birth and low birth weight infants: systematic review and meta-analyses

Births: final data for 2009.

Spontaneous preterm birth, a clinical dilemma: etiologic, pathophysiologic and genetic heterogeneities and racial disparity.

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