Low birth weight in Iran: Implications from a systematic review of the literature and meta-analysis in the period 1999-2017

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Abstract

Background: Low birth weight (LBW), a crucial determinant of neonatal complications, represents a major public health concern worldwide. Epidemiological research is of crucial importance for designing and implementing ad hoc interventions for this issue, helping and guiding decision- and policy-makers in each country to prevent the increased prevalence of LBW in infants through estimating the prevalence rate, identifying and controlling major risk factors. The present investigation aimed to systematically assess LBW prevalence rate in Iran and its determinants.

Methods: PubMed/Medline via Ovid, Embase, Web of Science and Scopus as well as Magiran, SID and Irandoc were searched from inception until November 2016. Also, the grey literature (via Google Scholar) was mined. The DerSimonian-Laird model was exploited. The I2 and Q-test tests were used to investigate heterogeneity between the studies. Sensitivity and subgroup analyses were performed to ensure the robustness and validity of our findings. Different cumulative meta-analyses were conducted stratifying according to the year of publication and sample size. Any potential bias in publication was assessed carrying out the Egger’s test.

Results: LBW prevalence rate was estimated to be 8% (95%CI: 7-9) in Iran. Sensitivity analysis confirmed the stability of finding. Studies were cumulated by the year of publication, and the results did not change pre- and post-cumulative meta-analysis. No publication bias could be observed.

Conclusion: LBW prevalence rate in Iran is well comparable with the prevalence figures of both developed and developing countries. This could be due to the health reforms implemented in Iran throughout the years.

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Most cited references 80

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Meta-analysis, funnel plots and sensitivity analysis.

Q Shi, Andrew J. Copas (2000)

Publication bias is a major problem, perhaps the major problem, in meta-analysis (or systematic reviews). Small studies are more likely to be published if their results are 'significant' than if their results are negative or inconclusive, and so the studies available for review are biased in favour of those with positive outcomes. Correcting for this bias is not possible without making untestable assumptions. In this paper, a sensitivity analysis is suggested which is based on fitting a model to the funnel plot. Some examples are discussed.

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Ambient Air Pollution and Low Birth Weight in Connecticut and Massachusetts

Michelle L. Bell, Keita Ebisu, Kathleen Belanger (2007)

Background Several studies have examined whether air pollution affects birth weight; however results vary and many studies were focused on Southern California or were conducted outside of the United States. Objectives We investigated maternal exposure to particulate matter with aerodynamic diameter < 10, < 2.5 μm (PM10, PM2.5), sulfur dioxide, nitrogen dioxide, and carbon monoxide and birth weight for 358,504 births in Massachusetts and Connecticut from 1999 to 2002. Methods Analysis included logistic models for low birth weight (< 2,500 g) and linear models with birth weight as a continuous variable. Exposure was assigned as the average county-level concentration over gestation and each trimester based on mother’s residence. We adjusted for gestational length, prenatal care, type of delivery, child’s sex, birth order, weather, year, and mother’s race, education, marital status, age, and tobacco use. Results An interquartile increase in gestational exposure to NO2, CO, PM10, and PM2.5 lowered birth weight by 8.9 g [95% confidence interval (CI), 7.0–10.8], 16.2 g (95% CI, 12.6–19.7), 8.2 g (95% CI, 5.3–11.1), and 14.7 g (95% CI, 12.3–17.1), respectively. Lower birth weight was associated with exposure in the third trimester for PM10, the first and third trimesters for CO, the first trimester for NO2 and SO2, and the second and third trimesters for PM2.5. Effect estimates for PM2.5 were higher for infants of black mothers than those of white mothers. Conclusions Results indicate that exposure to air pollution, even at low levels, may increase risk of low birth weight, particularly for some segments of the population.

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The fetal and childhood growth of persons who develop type 2 diabetes.

T Forsén, J Eriksson, J Tuomilehto … (2000)

Type 2 diabetes is associated with low birthweight followed by obesity in adulthood. Persons who develop the disease may therefore have a particular pattern of growth from birth through childhood. To examine the relation of type 2 diabetes to size at birth and childhood growth. Cohort study. Helsinki, Finland. Men (n = 3,639) and women (n = 3,447) who were bom at the Helsinki University Central Hospital between 1924 and 1933, who went to school in Helsinki, and who still lived in Finland in 1971. Detailed birth and school health records were available for all 7,086 participants. We identified 471 men and women who developed type 2 diabetes by using the national Social Insurance Institution's register of all persons in Finland who are receiving long-term therapy with medication. Incidence of diabetes ascertained from a national register. The main explanatory measurements were size at birth and childhood growth in terms of height, weight, and body mass index. The cumulative incidence of type 2 diabetes was 7.9% (n = 286) in men and 5.4% (n = 185) in women. The incidence increased with decreasing birthweight, birth length, ponderal index (birthweight/length(3)), and placental weight The odds ratio for type 2 diabetes was 1.38 (95% CI, 1.15 to 1.66; P < 0.001) for each 1-kg decrease in birthweight. The mean weights and heights of the children at 7 years of age who later developed type 2 diabetes were about average. Thereafter, their growth in weight and height was accelerated until 15 years of age. The odds ratio for development of type 2 diabetes was 1.39 (CI, 1.21 to 1.61; P < 0.001) for each standard deviation increase in weight between 7 and 15 years of age. The odds ratio became 1.83 (CI, 1.37 to 2.45; P< 0.001) in an analysis restricted to persons whose birthweights were below 3,000 g. Children of both sexes whose mothers had a high body mass index in pregnancy had more rapid growth during childhood and an increased incidence of type 2 diabetes. These findings are consistent with the hypothesis that type 2 diabetes is programmed in utero in association with low rates of fetal growth. The increased risk for type 2 diabetes associated with small size at birth is further increased by high growth rates after 7 years of age.

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Author and article information

Journal

Journal ID (nlm-ta): Med J Islam Repub Iran

Journal ID (iso-abbrev): Med J Islam Repub Iran

Journal ID (publisher-id): Med J Islam Repub Iran

Journal ID (publisher-id): MJIRI

Title: Medical Journal of the Islamic Republic of Iran

Publisher: Iran University of Medical Sciences

ISSN (Print): 1016-1430

ISSN (Electronic): 2251-6840

Publication date Collection: 2018

Publication date (Electronic): 13 February 2018

Volume: 32

Page: 13

Affiliations

¹ Student Research Committee, Department of Health Services Management, School of Health Management and Information Sciences, Iran University of Medical Sciences, Tehran, Iran.

² School of Public Health, Department of Health Sciences (DISSAL), University of Genoa, Genoa, Italy.

³ Section of History of Medicine and Ethics, Department of Health Sciences (DISSAL), University of Genoa, Genoa, Italy.

⁴ Department of Health Services Management, School of Health Management and Information Sciences, Iran University of Medical Sciences, Tehran, Iran.

⁵ Department of Epidemiology, Faculty of Health and Nutrition, Lorestan University of Medical Sciences, Khorramabad, Iran.

⁶ Health Management and Economics Research Center, Iran University of Medical Sciences, Tehran, Iran.

Author notes

Corresponding author: Dr Masoud Behzadifar, masoudbehzadifar@ 123456gmail.com

Article

DOI: 10.14196/mjiri.32.13

PMC ID: 6108244

PubMed ID: 30159264

SO-VID: b7d96028-6215-47ec-9c83-812f9da990d1

License:

This is an open-access article distributed under the terms of the Creative Commons Attribution NonCommercial 3.0 License (CC BY-NC 3.0), which allows users to read, copy, distribute and make derivative works for non-commercial purposes from the material, as long as the author of the original work is cited properly.

History

Date received : 31 May 2017

Page count

Figures: 6, Tables: 5, References: 93, Pages: 10

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