Elsevier

Women and Birth

Volume 32, Issue 6, December 2019, Pages e538-e543
Women and Birth

Sociodemographic factors associated with preterm birth and low birth weight: A cross-sectional study

https://doi.org/10.1016/j.wombi.2019.03.014Get rights and content

Abstract

Background

Preterm birth and low birth weight are two public health problems worldwide associated with higher morbidity and perinatal death risk.

Aims

To determine the incidence and socio-demographic factors associated with preterm birth and low birth weight in Spanish women.

Methods

Cross-sectional study with data from women who gave birth in Spain during 2015 extracted from the Statistical Bulletin of births (National Institute Statistics). Records analysed were 331,449. Single births from 22 weeks gestation and fetuses with weight ≥ 500 g were included. Unadjusted and adjusted odd ratios with 95% confidence interval in a multiple logistic regression model were calculated. Variables associated with both health problems were considered dependent variables.

Findings

Preterm birth rate in Spain was 6.7% and low birth weight rate was 7.3%. Socio-demographic variables associated with preterm birth were maternal age ≤19 years, immigrant mothers, educational level ≤ secondary studies, and women living in large cities. Low birth weight was related to maternal age ≤19 years and ≥35 years, educational level ≤ secondary studies, and single mothers. Not having previous children and caesarean births were associated with both risks.

Conclusions

The rates of both risks decreased in Spain, one of the countries in Europe where maternal age at having the first child has increased the most and with the lowest birth rate in the world. Maternal age, educational level, maternal nationality, marital status and population size were associated with one or both risks, so the results of this study could be especially relevant to the clinical practice.

Introduction

The World Health Organization (WHO) considers prematurity a global problem given its relationship with the risk of neonatal mortality. The WHO defines preterm birth (PTB) as one that occurs before 37 weeks of gestation1. Globally, around 11% of births were premature in 2010, which was about 15 million births, resulting in 1 million neonatal deaths1. Worldwide, premature birth is the leading cause of infant mortality in children under 5 years of age2; it is associated with an increased risk of heart defects, pulmonary disorders, cerebral palsy, and developmental delay3.

The WHO also defines low birth weight (LBW) as a newborn with a weight below 2500 g. This institution defines very LBW as being less than 1500 g, and extreme LBW when it is below 1000 g. LBW is a public health problem at a global level with short- and long-term consequences. Low birth weight is usually the consequence of PTB, growth retardation, or both, and it may occur in preterm or term newborns. It is estimated that between 15% and 20% of all births in the world are LBW births. The goal of the WHO is to achieve a 30% reduction in the number of babies born weighing less than 2500 g by 20254.

As with PTB, newborns with LBW have a much higher risk of perinatal death than newborns of normal weight5, 6, as well as a higher morbidity that translates into an increased risk of infections, growth restriction, neurological problems, cognitive delay, and learning disability7. There are many studies that associate PTB and LBW with problems such as cerebral palsy8. Developmental disabilities are pathologies that cause deficits in physical, cognitive, and behavioral functioning, in addition to speech disorders9.

In Europe, the rate of newborns with LBW ranged between 4 and 9%, with an average of 6.5%. Nordic countries had the lowest rate of LBW newborns. In Spain, this rate increased in 2010 compared to previous years such that the percentage of live births below 2500 g was 8.7%. Of these, 1% was born at a weight less than 1500 g, and the rest (7.7%) were between 1500 and 2499 g. Thus, Spain is in the group of countries with the highest rate of LBW births10.

Preterm birth rates remained stable in most European countries between 2004 and 2010 at approximately 5–10%. This was lower than in Nordic countries, and the highest percentages were recorded in Cyprus and Hungary. In Spain, the percentage of babies born alive as preterm births in 2010 was around 8%, which was a reduction of only 0.1% since 200410.

Different studies in Europe and U.S. suggest an association between birth weight and socioeconomic status11. Several authors have found an increased risk of LBW in immigrant mothers and smoking mothers12. Regarding risk factors of PTB, advanced maternal age, mothers under 19 years old13, a low level of maternal education12, 13, 14, or being a single mother have been cited14. In addition, in a recent study in China15 conducted in Jiang-a district (Wuhan) between 2011 and 2013, authors concluded that women living in rural areas were less likely to have preterm births; in this relationship, environmental factors could be decisive. A multi-country systematic review of 106 observational studies revealed how low socioeconomic status relates to adverse outcomes, such as PTB and LBW16. Maternal risk factors related to PTB and LBW include, among others, advanced maternal age, low maternal body mass index, short stature, low weight, smoking17, 18, and deficits in prenatal control (in terms of: “The prenatal variable was categorized according to the minimum number of prenatal doctor check-ups recommended for the gestational age of birth and the month when the prenatal visits began…”)13. Other authors found no relationship between PTB and LBW with regard to ethnicity, but they found an association with advanced maternal age and smoking19. Low birth weight is also related to being an immigrant mother12.

The aims of the present study were to determine the socio-demographic factors associated with the risk of preterm birth (PTB) and low birth weight (LBW) in Spain in 2015 and to calculate its incidence.

Section snippets

Design, population and setting of the study

This descriptive cross-sectional study was carried out using data from women who gave birth in Spain during 2015. The data were extracted from the Statistical Bulletin of births of the National Institute of Statistics of Spain20. These data were available and freely accessible on the National Institute of Statistics website. Therefore, when using secondary data, no report from the ethics committee was required in accordance with Spanish legislation. The study population consisted of records of

Results

After discarding multiple births from the analysis and those births that occurred with birth weights of less than 22 weeks of gestation and / or with fetuses weighing less than 500 g, the total population of the study was 331,449 (n = 331,449). Of these, 18,847 (5.7%) were premature births (<37 weeks), and 20,434 (6.2%) births resulted in LBW fetuses (<2500 g). Among births with LBW fetuses, 10,203 (50%) were at full-term (≥37 weeks), while the other 50% occurred at gestation time points of

Discussion

This study shows a clear reduction in the incidence rates of both PTB (from 8% in 2010 to 6.7% in 2015) and LBW (from 8.7% in 2010 to 7.3% in 2015). Socio-demographic factors associated with PTB were young mothers, with level of education ≤ secondary studies, immigrant mothers and women living in large cities. Low birth weight was associated to young mothers and mothers aged 35 or older, with level of education ≤ secondary studies, and single mothers.

Among the socio-demographic factors

Conclusions

In conclusion, the incidence of PTB and LBW has decreased in recent years in Spain, and they are associated with women up to 19 year of age, women with educational level ≤ secondary studies and who have not previously had children. In addition, prematurity rates were higher for women living in large urban centers and for foreign mothers. The risk of having a newborn with LBW also correlated with mothers aged 35 years and those who were unmarried.

The current study provides more evidence about

Contribution to authorship

The first author conceived the idea of this study, performed the study design and data analysis, and drafted the manuscript. One co-author contributed to data extraction, data analysis and manuscript writing. Other co-author contributed to data extraction, review the data analysis and the interpretation of the data. Other co-author contributed to manuscript writing, data extraction and review the methodology. Other co-author contributed to interpretation of the data and revised the manuscript

Author agreement stating

This article is the authors original work and it has not received prior publication and is not under consideration for publication elsewhere; all authors have seen and approved the manuscript being submitted; the authors abide by the copyright terms and conditions of Elsevier and the Australian College of Midwives.

Conflict of interest

All authors declare no any actual or potential conflict of interest, including financial and personal relationships with people or organizations within three years of beginning the submitted work.

Ethical statement

Is not applicable.

Funding

We received no funding for this study.

Acknowledgements and disclosures

None declared.

References (30)

  • C.A. Boyle et al.

    Trends in the prevalence of developmental disabilities in US children 1997–2008

    Pediatrics

    (2011)
  • EURO-PERISTAT Project with SCPE and EUROCAT. European Perinatal Health Report (2010). The health and care of pregnant...
  • M. Heaman et al.

    Risk factors for preterm birth and small-for-gestational-age births among Canadian women

    Paediatr Perinat Epidemiol

    (2013)
  • L.L. Oliveira et al.

    Maternal and neonatal factors related to prematurity

    Rev Esc Enferm USP

    (2016)
  • A.M. Oftedal et al.

    Socio-economic risk factors for preterm birth in Norway 1999–2009

    Scand J Public Health

    (2016)
  • Cited by (53)

    View all citing articles on Scopus
    View full text