# Prevalence and Determinants of Low Birth Weight in Ethiopia: A Systematic Review and Meta-Analysis

Authors: Nuradin Abusha Katiso; Getachew Mullu Kassa; Gedefaw Abeje Fekadu; Abadi Kidanemariam Berhe; Achenef Asmamaw Muche
Journal: Advances in Public Health
 (2020)

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## Abstract

Introduction. Low birth weight (LBW) is the most significant risk factor for neonatal and infant mortality. It is one of the major public health problems in developing countries. Although there are various studies on low birth weight, findings were inconsistent and inconclusive. Therefore, this study was conducted to estimate the national-pooled prevalence of low birth weight and its associated factors in Ethiopia. Method. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline was followed. This meta-analysis employed a review of both published and unpublished studies conducted in Ethiopia. The databases used were PubMed, Google Scholar, CINAHL, and African Journals Online. Relevant search terms for prevalence and determinants of LBW were used to retrieve articles. The meta-analysis was conducted using STATA 14 software. Forest plots were used to present the findings. The Cochran Q test and I2 test statistics were used to test heterogeneity across studies. Egger’s test was used to assess the publication bias of included studies. The pooled prevalence and the odds ratios (OR) with 95% confidence intervals (CI) were computed and were presented using forest plots. Results. A total of 28 studies, 50,110 newborn babies, were included in this meta-analysis. The pooled prevalence of LBW in Ethiopia was 14.1% (95% CI = 11.2, 17.1). Higher variation in the prevalence of LBW in different regions across the country was observed. Significant association of LBW with sex of the newborn baby, higher odds among female babies (OR = 1.5 (95% CI = 1.2, 1.7)), prematurity (OR = 4.7 (95% CI = 1.5, 14.5)), not attending prenatal care (OR = 1.7 (95% CI = 1.4, 2.2)), pregnancy-induced hypertension (OR = 6.7 (95% CI = 3.5, 12.9)), and newborn babies whose mothers were from rural areas (OR = 1.8 (95% CI = 1.2, 2.6) were the factors associated with low birth weight. Conclusions. The prevalence of LBW in Ethiopia was high. LBW was associated with several maternal and newborn characteristics. The large disparity of LBW among the different regions in the country needs targeted intervention in areas with higher prevalence. Particular emphasis should be given to mothers residing in rural areas. Community-based programs are important to increase the use of prenatal care.


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## Body

## 1. Introduction

World Health Organization (WHO) defined low birth weight (LBW) as infants whose weight is less than 2500 gram at birth irrespective of gestational age [1]. It is one of the major public health problems globally, with a higher prevalence in developing countries [1–4]. Reports showed that 16% of all births globally were low birth weight, representing more than 20 million births a year [5, 6]. Furthermore, LBW is a significant predictor of prenatal mortality and morbidity, especially in sub-Saharan African countries. It is also associated with a range of short- and long-term consequences including chronic disease in later life [1–5, 7].Several studies identified prematurity and intrauterine growth restriction as predominant causes of low birth weight. Prematurity is the leading reason in developed countries, whereas intrauterine growth restriction is in developing ones [1, 6, 8]. Additionally, inadequate weight gain during pregnancy, low prepregnancy weight, short stature, sex of the newborn (being female), hard physical work during pregnancy, illness(especially infections), the lower status of women, and lack of antenatal care (ANC) are also identified as risk factors for low birth weight in developing countries [9–12]. Multiple gestations, young maternal age, primiparity, low education level, poor maternal nutrition before and during pregnancy, and lower maternal anthropometric measurements are also associated with low birth weight [13–20].Various studies were conducted to estimate the prevalence and determinants of low birth weight in Ethiopia. The prevalence of low birth weight in various studies conducted in Ethiopia ranged from 6% to 29.1% [21–47]. Additionally, sex of the infant, pregnancy-induced hypertension, ANC follow-up, prematurity, parity, and residence were found to be associated with low birth weight [21–50].However, most of these studies found inconclusive findings, especially on the factors associated with LBW. Moreover, most of the available studies in Ethiopia were conducted using small sample size limited to a certain region or area. Therefore, this study was conducted to pool the available studies in the country and to present the national estimate of LBW and selected factors associated with it. The findings of this study will be important to design better health policies to prevent LBW and to design policies which can target the identified factors. Additionally, it will assist the country to provide information that can suggest areas of intervention and help achieve the national and international maternal and child health-related goals and targets.


## 2. Methods

### 2.1. Study Design and Search Strategy/Data Sources

A systemic review and meta-analysis on the prevalence and determinant factors of low birth weight in Ethiopia were performed using the published and unpublished research articles. Major databases such as PubMed, Google Scholar, CINAHL, and African Journals Online (AJOL) were used to review published studies. In addition, we have used Google to retrieve unpublished studies from the official website of Addis Ababa University electronic database [51]. All published articles up to July 30, 2017 were included in this review. The reference list of already identified studies was also searched to retrieve additional articles. The online search was carried out using the following search terms and phrase: “prevalence of low birth weight, low birth weight, abnormal birth weight, newborn, neonate, underweight, infant, factors affecting low birth weight; pregnancy-induced hypertension (PIH) and low birth weight, parity and low birth weight, ANC and LBW, preterm delivery and LBW, and residence and LBW, Ethiopia” separately, and/or in combination using the Boolean operators to fit PubMed database, the following search strategy was applied: birth weight [MeSH Term] OR low birth weight OR abnormal birth weight OR normal birth weight OR underweight OR big baby weight OR macrosomia AND newborn [MeSH Term] OR neonate OR infant AND Ethiopia.


### 2.2. Study Selection and Eligibility Criteria

The following criteria were used to include and exclude studies from the review.


#### 2.2.1. Inclusion Criteria

(i)
Participants: this review included all studies, irrespective of characteristics of participants, that were conducted on prevalence and factors associated with low birth weight in Ethiopia(ii)
Setting: all studies conducted in community or institution level(iii)
Definition: all research studies that define LBW as birth weight less than 2,500 grams(iv)
Publication types: journal articles, master’s thesis, and dissertations(v)
Studies published only in the English language were included in the review(vi)
Timeframe: all studies irrespective of the time of data collection or publication were included


#### 2.2.2. Exclusion Criteria

(i)
Research studies that did not report outcome variable of this review were excluded(ii)
Qualitative studies were excluded from the analysis(iii)
Studies with methodological problems and review articles were also excluded from the review


### 2.3. Data Extraction

The data extraction was performed by five researchers using a data extraction tool. The researcher developed the data extraction tool. The tool included information on the name of the author, publication year, study design, data collection period, sample size, study area, the age of study participants, response rate, the definition used for low birth weight, the prevalence of low birth weight, and maternal and newborn-associated factors.


### 2.4. Quality Assessment and Data Collection

Retrieved articles were assessed for inclusion using their title and abstract, and then, a full review of articles for quality assessment was performed before selecting for final review. Researchers used the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI) for critical appraisal. Two reviewers independently assessed the articles for inclusion in the review using the instrument. The disagreement (on article selection and data extraction), which arose between the reviewers, was resolved through discussion and by involving a third reviewer. The quality of all studies included in this review after the final full article review was also assessed.


### 2.5. Publication Bias and Heterogeneity

Publication bias and heterogeneity were also assessed. Egger’s test was used to check the publication bias of studies. Statistically significant publication bias was declared at ap value less than 0.05. The heterogeneity of studies was tested using I2 test statistics. I2 test statistics result of 25%, 50%, and 75% was declared as low, moderate, and high heterogeneity, respectively. The random effect model was used for meta-analysis test results, which indicates statistically significant heterogeneity. Also, trim and fill analysis was conducted for studies with statistically significant publication bias using the random effect methods of analysis.


### 2.6. Statistical Methods and Analysis

The analysis was conducted using STATA version 14 software. The forest plot was used to present the combined estimate and odds ratio (OR) with the 95% confidence interval. For studies, which did not present standard error (SE), it was calculated using the formulaSE=px1−p/n. The calculated standard error and prevalence rate of each study was then entered into STATA software to calculate the overall prevalence and its 95% CI. The pooled OR was used to show the effect of sex of neonates, pregnancy-induced hypertension, antenatal care booking, gestational age, parity, residence, and pregnancy intention on low birth weight.


## 2.1. Study Design and Search Strategy/Data Sources

A systemic review and meta-analysis on the prevalence and determinant factors of low birth weight in Ethiopia were performed using the published and unpublished research articles. Major databases such as PubMed, Google Scholar, CINAHL, and African Journals Online (AJOL) were used to review published studies. In addition, we have used Google to retrieve unpublished studies from the official website of Addis Ababa University electronic database [51]. All published articles up to July 30, 2017 were included in this review. The reference list of already identified studies was also searched to retrieve additional articles. The online search was carried out using the following search terms and phrase: “prevalence of low birth weight, low birth weight, abnormal birth weight, newborn, neonate, underweight, infant, factors affecting low birth weight; pregnancy-induced hypertension (PIH) and low birth weight, parity and low birth weight, ANC and LBW, preterm delivery and LBW, and residence and LBW, Ethiopia” separately, and/or in combination using the Boolean operators to fit PubMed database, the following search strategy was applied: birth weight [MeSH Term] OR low birth weight OR abnormal birth weight OR normal birth weight OR underweight OR big baby weight OR macrosomia AND newborn [MeSH Term] OR neonate OR infant AND Ethiopia.


## 2.2. Study Selection and Eligibility Criteria

The following criteria were used to include and exclude studies from the review.


### 2.2.1. Inclusion Criteria

(i)
Participants: this review included all studies, irrespective of characteristics of participants, that were conducted on prevalence and factors associated with low birth weight in Ethiopia(ii)
Setting: all studies conducted in community or institution level(iii)
Definition: all research studies that define LBW as birth weight less than 2,500 grams(iv)
Publication types: journal articles, master’s thesis, and dissertations(v)
Studies published only in the English language were included in the review(vi)
Timeframe: all studies irrespective of the time of data collection or publication were included


### 2.2.2. Exclusion Criteria

(i)
Research studies that did not report outcome variable of this review were excluded(ii)
Qualitative studies were excluded from the analysis(iii)
Studies with methodological problems and review articles were also excluded from the review


## 2.2.1. Inclusion Criteria

(i)
Participants: this review included all studies, irrespective of characteristics of participants, that were conducted on prevalence and factors associated with low birth weight in Ethiopia(ii)
Setting: all studies conducted in community or institution level(iii)
Definition: all research studies that define LBW as birth weight less than 2,500 grams(iv)
Publication types: journal articles, master’s thesis, and dissertations(v)
Studies published only in the English language were included in the review(vi)
Timeframe: all studies irrespective of the time of data collection or publication were included


## 2.2.2. Exclusion Criteria

(i)
Research studies that did not report outcome variable of this review were excluded(ii)
Qualitative studies were excluded from the analysis(iii)
Studies with methodological problems and review articles were also excluded from the review


## 2.3. Data Extraction

The data extraction was performed by five researchers using a data extraction tool. The researcher developed the data extraction tool. The tool included information on the name of the author, publication year, study design, data collection period, sample size, study area, the age of study participants, response rate, the definition used for low birth weight, the prevalence of low birth weight, and maternal and newborn-associated factors.


## 2.4. Quality Assessment and Data Collection

Retrieved articles were assessed for inclusion using their title and abstract, and then, a full review of articles for quality assessment was performed before selecting for final review. Researchers used the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI) for critical appraisal. Two reviewers independently assessed the articles for inclusion in the review using the instrument. The disagreement (on article selection and data extraction), which arose between the reviewers, was resolved through discussion and by involving a third reviewer. The quality of all studies included in this review after the final full article review was also assessed.


## 2.5. Publication Bias and Heterogeneity

Publication bias and heterogeneity were also assessed. Egger’s test was used to check the publication bias of studies. Statistically significant publication bias was declared at ap value less than 0.05. The heterogeneity of studies was tested using I2 test statistics. I2 test statistics result of 25%, 50%, and 75% was declared as low, moderate, and high heterogeneity, respectively. The random effect model was used for meta-analysis test results, which indicates statistically significant heterogeneity. Also, trim and fill analysis was conducted for studies with statistically significant publication bias using the random effect methods of analysis.


## 2.6. Statistical Methods and Analysis

The analysis was conducted using STATA version 14 software. The forest plot was used to present the combined estimate and odds ratio (OR) with the 95% confidence interval. For studies, which did not present standard error (SE), it was calculated using the formulaSE=px1−p/n. The calculated standard error and prevalence rate of each study was then entered into STATA software to calculate the overall prevalence and its 95% CI. The pooled OR was used to show the effect of sex of neonates, pregnancy-induced hypertension, antenatal care booking, gestational age, parity, residence, and pregnancy intention on low birth weight.


## 3. Results

### 3.1. Study Selection

This systematic review and meta-analysis included all published and unpublished studies on LBW conducted in Ethiopia. Search for articles using databases resulted in a total of 1,004 articles. After screening all articles using their title, abstract, and full paper review, a total of 28 articles were selected for the final meta-analysis (Figure1).Figure 1
Flow diagram of the studies included in the meta-analysis.


### 3.2. Characteristics of Included Studies

The mean birth weight of babies included in the review ranged from 2,077 to 3,147 grams, and the sample size ranges from 253 to 11,872. Overall, this review included a total of 50,110 newborn babies (Table1). The majority [17] of the included studies were cross-sectional, 8 were cohort, and 3 were case-control studies. Most of the regions in Ethiopia (Oromia, Amhara, Tigray, SNNPR regions, Addis Ababa city, and Dire Dawa city) were represented in this review. Two of the studies were nation-based studies. The publication year of the studies was from 1990 to 2017 (Table 2).Table 1
Summary characteristics of studies included in the meta-analysis to show the prevalence of low birth weight in Ethiopia.
S. No.Author, publication yearStudy designYear study conductedSample sizeStudy areaMean birth weight (in grams)Prevalence of LBW (95% CI)1Zenebe et al, 2014 [46]Institution-based cross-sectionalMarch–May, 2012.540Gondar town, Amhara region290017.4 (14.2, 20.6)2Wado et al, 2014 [43]Community-based prospective cohortJune 2012–February 2013537Oromia region298917.9 (14.66, 21.14)3Teklehaimanot et al, 2014 [39]Institution-based cross-sectionalFebruary–April, 2013.253Axum, Tigray region30559.9 (6.22, 13.58)4Tema, 2006 [40]Institution-based cross-sectionalSeptember 1st, 2002–March 30th, 2003645Jimma, Oromia region—22.5 (19.28, 25.72)5Gebremedhin et al, 2015 [29]Institution-based cross-sectionalAug 2–Sep 12, 2013308Tigray region3094.914.6 (10.66, 18.54)6Zeleke et a, 2012 [45]Institution-based cross-sectionalMay 1–July 30, 2010.305Gondar town, Amhara region297217.1 (12.87, 21.33)7Adane et al, 2014 [22]Institution-based cross-sectional studyFebruary 2013481Gondar University Hospital, Amhara2977.711.2 (8.38, 14.02)8Demelash et al, 2015 [49]Case-control studyApril 1st–August 30th, 2013387Bale Zone, Oromia region——9Assefa et al, 2012 [25]Cohort studyDecember 2009–November 2010956Kersa, Oromia region—28.3 (25.44, 31.16)10Gebremedhin et al, 2012 [29]Community-based prospective cohortJanuary–October 2011575Sidama Zone, SNNPR289616.5 (13.47, 19.53)11Desalegn, 2015 [50]Case-control studyFebruary to June 2015Case = 147, control = 294Debre Berehan Referral hospital, Amhara regionCase = 2077.55 control = 3230.0—12Teshome et al, 2006 [41]Institution-based prospective study2006373Gondor, Amhara region3 00315.4 (11.74, 19.06)13Madebo, 1994 [33]Retrospective study1989–19901,260Sidama Zone, SNNPR3,2438 (6.5, 9.5)14Zerfu et al, 2016 [47]Prospective cohort study—374Arsi Zone, Oromia region—9.1 (6.19, 12.01)15Gebremariam, 2005 [28]Cross-sectional1999–20001441Jimma Hospital, Oromia region—10.02 (8.47, 11.57)16Nekatibeb and Mariam, 2007 [36]Cross-sectional20051832Metu Karl Hospital, Oromia regions31478.6 (7.32, 9.88)17Feleke and Enquoselassie, 1999 [27]Prospective study1996–19974206Addis Ababa30659.1 (8.23, 9.97)18Assefa et al, 2004 [25]Community-based longitudinal study1992–11947,586Jimma, Illubaborand Keffa, Oromia, and SNNPR306610.0 (9.33, 10.67)19Enquoselassie and Minyilshewa, 2000 [26]Retrospective study1976–19969975Tikure Anbasa, Addis Ababa31268.4 (7.86, 8.94)20Mengesha et al, 2017 [34]Cross-sectional survey20141152Tigray region—10.5 (8.73, 12.27)21Abdo and Tesso, 2016 [21]Facility-based cross-sectional2015327Hosanna town, SNNPR—9.8 (6.58, 13.02)22Tigistu, 2016 [42]Facility-based cross-sectional2016403Dire Dawa town310613.2 (9.9, 16.5)23Mihiretu 2017 [35]Facility-based cross-sectional study2015300Wolaita Sodo Referral Hospital, SNNPR—6 (3.31, 8.69)24Aman Yesuf et al, 2016 [48]Case–control study2013453Gondar and Bahirdar Referral Hospital——25Zerfu et al, 2016 [47]In-depth analysis EDHS201111, 872In-depth analysis of EDHS 2011—29.1 (28.28, 29.92)26Kebede and Larson, 1994 [32]Retrospective cohort1985–19882259Jimma Regional Hospital, Oromia233213.1 (11.71, 14.49)27Hadush et al, 2017 [31]Facility-based cross-sectional study2017422Mekelle, Tigray280727 (22.76, 31.24)28Sheferaw, 1990 [38]Retrospective cross-sectional1986–19881707Jimma hospital, Oromia318312.3 (10.74, 13.86)Table 2
Subgroup analysis of prevalence of low birth weight in Ethiopia.
SubgroupNumber of studies includedPrevalence (95% CI)Test of heterogeneity (I2)p valueBy regionAddis Ababa city28.66 (8.00, 9.33)44.1%0.181Amhara415.12 (11.99, 18.26)70.1%0.018Dire Dawa city113.20 (09.90, 16.50)——Oromia815.09 (11.33, 18.85)96.8%<0.001SNNPR409.99 (06.02, 13.96)90.1%<0.001Tigray415.36 (08.57, 22.15)94.3%<0.001Nation-based studies219.55 (00.83, 38.27)99.9%<0.001By study designCross-sectional study1714.55 (10.06, 19.03)98.8%<0.001Cohort study813.03 (10.62, 15.45)97.0%<0.001By publication year1990–2000510.12 (8.37, 11. 86)92.9%<0.0012001–2010512.82 (9.93, 15.70)94.3%<0.0012011–20171515.84 (10.63, 21.05)98.5%<0.001The quality of included studies was assessed using a quality assessment toot based on the JBI critical appraisal tool checklists for cross-sectional (19 studies), case-control (3 studies), and cohort (7 studies). Accordingly, the quality score of studies that used a cross-sectional study design ranged from 75% to 93.75%. For research studies that used cohort study design, the quality score ranged from 64% to 77%, and for case-control studies, the quality score ranged from 72% to 89% (Additional files 1–3).


### 3.3. Prevalence of Low Birth Weight

The prevalence of LBW ranged from 6% to 29.1%. The highest prevalence of LBW was observed in Tigray region (15.4% (95% CI = 08.6, 22.2)) and the lowest was in Addis Ababa city (8.7% (95% CI = 8.0, 9.3)). The final pooled prevalence of LBW in Ethiopia was 14.1% (95% CI = 11.2, 17.1). TheI2 test result showed the presence of high heterogeneity (I2 = 98.9%, p value =< 0.001). To address this heterogeneity, the random effect method of analysis was used for the meta-analysis (Figure 2).Figure 2
Forest plot displaying the pooled prevalence of low birth weight in Ethiopia.


### 3.4. Sex Difference in LBW

Seven of the studies included in this review showed that the sex of the newborn is associated with low birth weight [24, 25, 30, 39, 45–47]. In four studies, there was no significant difference in birth weight and sex of the newborn [26, 34, 43, 48]. However, the final pooled estimate showed that female newborn babies are at a higher risk of low birth weight than males, OR = 1.46 (95% CI = 1.22, 1.73) (Figure 3).Figure 3
Forest plot displaying the association of sex of the newborn and low birth weight in Ethiopia.


### 3.5. Prenatal Care and LBW

A total of 14 studies were included in this category of meta-analysis [22, 24–26, 30, 34, 40, 43, 45–50]. Eight of these studies showed a significant association between the absence of antenatal follow-up with a higher risk of LBW [24, 34, 40, 43, 45, 47–49]. Altogether, this meta-analysis showed that babies born from women who had no prenatal care were 1.7 times more likely to have low birth weight babies, OR = 1.72 (95% CI = 1.35, 2.2) (Figure 4).Figure 4
Forest plot displaying the association of absence of prenatal care and low birth weight of the newborn in Ethiopia.


### 3.6. Preterm Delivery and LBW

Six of the studies included in this meta-analysis showed that preterm babies (delivered before 37 weeks of gestation) were more likely to be low birth weight [29, 34, 40, 45, 46, 50]. While one study showed the opposite finding [22], and one study showed no difference in prevalence of LBW between preterm and term babies [26]. This meta-analysis showed a significant association between preterm delivery and low birth weight, OR = 4.7 (95% CI = 1.53, 14.42) (Figure 5).Figure 5
Forest plot displaying the association of preterm delivery before 37 weeks of gestation and low birth weight Ethiopia.


### 3.7. Pregnancy-Induced Hypertension and LBW

Five studies were included in this category of meta-analysis [22, 39, 43, 46, 50]. The pooled meta-analysis showed the presence of an association between pregnancy-induced hypertension and low birth weight, OR = 6.7 (95% CI = 3.48, 12.92) (Figure 6).Figure 6
Forest plot displaying the association of pregnancy-induced hypertension on low birth weight in Ethiopia.


### 3.8. Parity and LBW

Ten studies were included in this category of meta-analysis [22, 24–26, 30, 34, 43, 45, 48, 50]. The final pooled meta-analysis showed no statistically significant difference in the rate of LBW among women who were primipara and multipara, OR = 1.2 (95% CI = 0.9, 1.5) (Figure 7).Figure 7
Forest plot displaying the association of being primipara and low birth weight in Ethiopia.


### 3.9. Residence and LBW

From 13 studies included in this category of meta-analysis [22,24–26, 29, 34, 40, 43, 45–49], two studies showed higher LBW risk among babies born from urban resident mothers [34, 40]. But, nine studies showed an increased risk of LBW among rural residents [24–26, 29, 43, 46–49]. Two studies showed no statistically significant difference in the rate of LBW among rural and urban resident mothers [22, 45]. The final pooled meta-analysis showed that babies born from rural mothers were at a higher risk of low birth weight compared to those born from an urban area, OR = 1.75 (95% CI = 1.19, 2.56) (Figure 8).Figure 8
Forest plot displaying the association of rural residence and low birth weight in Ethiopia.


### 3.10. Heterogeneity and Publication Bias

Egger’s test was conducted to assess the publication bias of studies included in this meta-analysis. Accordingly, nonsignificant publication bias was observed in all categories of meta-analysis,p value >0.05. For studies that present with high heterogeneity between studies, the random effect method of analysis was used.


### 3.11. Meta-Regression

The meta-analysis showed evidence of heterogeneity of included studies, and therefore, meta-regression was conducted to assess the source of heterogeneity. However, none of the covariates tested for source of heterogeneity were statistically significant. Therefore, the heterogeneity could be explained by other variables not included in this meta-analysis (Table3).Table 3
Meta-regression analysis of the different study-level covariates explaining possible sources of heterogeneity.
Study characteristicsCoefficientp valuePublication year0.2270.162Sample size<0.0010.578Cohort study design−1.2190.671Addis Ababa city−4.450.595Amhara2.0420.791Oromia1.9380.790SNNPR−3.1570.681Tigray2.1580.779National study6.3440.451


## 3.1. Study Selection

This systematic review and meta-analysis included all published and unpublished studies on LBW conducted in Ethiopia. Search for articles using databases resulted in a total of 1,004 articles. After screening all articles using their title, abstract, and full paper review, a total of 28 articles were selected for the final meta-analysis (Figure1).Figure 1
Flow diagram of the studies included in the meta-analysis.


## 3.2. Characteristics of Included Studies

The mean birth weight of babies included in the review ranged from 2,077 to 3,147 grams, and the sample size ranges from 253 to 11,872. Overall, this review included a total of 50,110 newborn babies (Table1). The majority [17] of the included studies were cross-sectional, 8 were cohort, and 3 were case-control studies. Most of the regions in Ethiopia (Oromia, Amhara, Tigray, SNNPR regions, Addis Ababa city, and Dire Dawa city) were represented in this review. Two of the studies were nation-based studies. The publication year of the studies was from 1990 to 2017 (Table 2).Table 1
Summary characteristics of studies included in the meta-analysis to show the prevalence of low birth weight in Ethiopia.
S. No.Author, publication yearStudy designYear study conductedSample sizeStudy areaMean birth weight (in grams)Prevalence of LBW (95% CI)1Zenebe et al, 2014 [46]Institution-based cross-sectionalMarch–May, 2012.540Gondar town, Amhara region290017.4 (14.2, 20.6)2Wado et al, 2014 [43]Community-based prospective cohortJune 2012–February 2013537Oromia region298917.9 (14.66, 21.14)3Teklehaimanot et al, 2014 [39]Institution-based cross-sectionalFebruary–April, 2013.253Axum, Tigray region30559.9 (6.22, 13.58)4Tema, 2006 [40]Institution-based cross-sectionalSeptember 1st, 2002–March 30th, 2003645Jimma, Oromia region—22.5 (19.28, 25.72)5Gebremedhin et al, 2015 [29]Institution-based cross-sectionalAug 2–Sep 12, 2013308Tigray region3094.914.6 (10.66, 18.54)6Zeleke et a, 2012 [45]Institution-based cross-sectionalMay 1–July 30, 2010.305Gondar town, Amhara region297217.1 (12.87, 21.33)7Adane et al, 2014 [22]Institution-based cross-sectional studyFebruary 2013481Gondar University Hospital, Amhara2977.711.2 (8.38, 14.02)8Demelash et al, 2015 [49]Case-control studyApril 1st–August 30th, 2013387Bale Zone, Oromia region——9Assefa et al, 2012 [25]Cohort studyDecember 2009–November 2010956Kersa, Oromia region—28.3 (25.44, 31.16)10Gebremedhin et al, 2012 [29]Community-based prospective cohortJanuary–October 2011575Sidama Zone, SNNPR289616.5 (13.47, 19.53)11Desalegn, 2015 [50]Case-control studyFebruary to June 2015Case = 147, control = 294Debre Berehan Referral hospital, Amhara regionCase = 2077.55 control = 3230.0—12Teshome et al, 2006 [41]Institution-based prospective study2006373Gondor, Amhara region3 00315.4 (11.74, 19.06)13Madebo, 1994 [33]Retrospective study1989–19901,260Sidama Zone, SNNPR3,2438 (6.5, 9.5)14Zerfu et al, 2016 [47]Prospective cohort study—374Arsi Zone, Oromia region—9.1 (6.19, 12.01)15Gebremariam, 2005 [28]Cross-sectional1999–20001441Jimma Hospital, Oromia region—10.02 (8.47, 11.57)16Nekatibeb and Mariam, 2007 [36]Cross-sectional20051832Metu Karl Hospital, Oromia regions31478.6 (7.32, 9.88)17Feleke and Enquoselassie, 1999 [27]Prospective study1996–19974206Addis Ababa30659.1 (8.23, 9.97)18Assefa et al, 2004 [25]Community-based longitudinal study1992–11947,586Jimma, Illubaborand Keffa, Oromia, and SNNPR306610.0 (9.33, 10.67)19Enquoselassie and Minyilshewa, 2000 [26]Retrospective study1976–19969975Tikure Anbasa, Addis Ababa31268.4 (7.86, 8.94)20Mengesha et al, 2017 [34]Cross-sectional survey20141152Tigray region—10.5 (8.73, 12.27)21Abdo and Tesso, 2016 [21]Facility-based cross-sectional2015327Hosanna town, SNNPR—9.8 (6.58, 13.02)22Tigistu, 2016 [42]Facility-based cross-sectional2016403Dire Dawa town310613.2 (9.9, 16.5)23Mihiretu 2017 [35]Facility-based cross-sectional study2015300Wolaita Sodo Referral Hospital, SNNPR—6 (3.31, 8.69)24Aman Yesuf et al, 2016 [48]Case–control study2013453Gondar and Bahirdar Referral Hospital——25Zerfu et al, 2016 [47]In-depth analysis EDHS201111, 872In-depth analysis of EDHS 2011—29.1 (28.28, 29.92)26Kebede and Larson, 1994 [32]Retrospective cohort1985–19882259Jimma Regional Hospital, Oromia233213.1 (11.71, 14.49)27Hadush et al, 2017 [31]Facility-based cross-sectional study2017422Mekelle, Tigray280727 (22.76, 31.24)28Sheferaw, 1990 [38]Retrospective cross-sectional1986–19881707Jimma hospital, Oromia318312.3 (10.74, 13.86)Table 2
Subgroup analysis of prevalence of low birth weight in Ethiopia.
SubgroupNumber of studies includedPrevalence (95% CI)Test of heterogeneity (I2)p valueBy regionAddis Ababa city28.66 (8.00, 9.33)44.1%0.181Amhara415.12 (11.99, 18.26)70.1%0.018Dire Dawa city113.20 (09.90, 16.50)——Oromia815.09 (11.33, 18.85)96.8%<0.001SNNPR409.99 (06.02, 13.96)90.1%<0.001Tigray415.36 (08.57, 22.15)94.3%<0.001Nation-based studies219.55 (00.83, 38.27)99.9%<0.001By study designCross-sectional study1714.55 (10.06, 19.03)98.8%<0.001Cohort study813.03 (10.62, 15.45)97.0%<0.001By publication year1990–2000510.12 (8.37, 11. 86)92.9%<0.0012001–2010512.82 (9.93, 15.70)94.3%<0.0012011–20171515.84 (10.63, 21.05)98.5%<0.001The quality of included studies was assessed using a quality assessment toot based on the JBI critical appraisal tool checklists for cross-sectional (19 studies), case-control (3 studies), and cohort (7 studies). Accordingly, the quality score of studies that used a cross-sectional study design ranged from 75% to 93.75%. For research studies that used cohort study design, the quality score ranged from 64% to 77%, and for case-control studies, the quality score ranged from 72% to 89% (Additional files 1–3).


## 3.3. Prevalence of Low Birth Weight

The prevalence of LBW ranged from 6% to 29.1%. The highest prevalence of LBW was observed in Tigray region (15.4% (95% CI = 08.6, 22.2)) and the lowest was in Addis Ababa city (8.7% (95% CI = 8.0, 9.3)). The final pooled prevalence of LBW in Ethiopia was 14.1% (95% CI = 11.2, 17.1). TheI2 test result showed the presence of high heterogeneity (I2 = 98.9%, p value =< 0.001). To address this heterogeneity, the random effect method of analysis was used for the meta-analysis (Figure 2).Figure 2
Forest plot displaying the pooled prevalence of low birth weight in Ethiopia.


## 3.4. Sex Difference in LBW

Seven of the studies included in this review showed that the sex of the newborn is associated with low birth weight [24, 25, 30, 39, 45–47]. In four studies, there was no significant difference in birth weight and sex of the newborn [26, 34, 43, 48]. However, the final pooled estimate showed that female newborn babies are at a higher risk of low birth weight than males, OR = 1.46 (95% CI = 1.22, 1.73) (Figure 3).Figure 3
Forest plot displaying the association of sex of the newborn and low birth weight in Ethiopia.


## 3.5. Prenatal Care and LBW

A total of 14 studies were included in this category of meta-analysis [22, 24–26, 30, 34, 40, 43, 45–50]. Eight of these studies showed a significant association between the absence of antenatal follow-up with a higher risk of LBW [24, 34, 40, 43, 45, 47–49]. Altogether, this meta-analysis showed that babies born from women who had no prenatal care were 1.7 times more likely to have low birth weight babies, OR = 1.72 (95% CI = 1.35, 2.2) (Figure 4).Figure 4
Forest plot displaying the association of absence of prenatal care and low birth weight of the newborn in Ethiopia.


## 3.6. Preterm Delivery and LBW

Six of the studies included in this meta-analysis showed that preterm babies (delivered before 37 weeks of gestation) were more likely to be low birth weight [29, 34, 40, 45, 46, 50]. While one study showed the opposite finding [22], and one study showed no difference in prevalence of LBW between preterm and term babies [26]. This meta-analysis showed a significant association between preterm delivery and low birth weight, OR = 4.7 (95% CI = 1.53, 14.42) (Figure 5).Figure 5
Forest plot displaying the association of preterm delivery before 37 weeks of gestation and low birth weight Ethiopia.


## 3.7. Pregnancy-Induced Hypertension and LBW

Five studies were included in this category of meta-analysis [22, 39, 43, 46, 50]. The pooled meta-analysis showed the presence of an association between pregnancy-induced hypertension and low birth weight, OR = 6.7 (95% CI = 3.48, 12.92) (Figure 6).Figure 6
Forest plot displaying the association of pregnancy-induced hypertension on low birth weight in Ethiopia.


## 3.8. Parity and LBW

Ten studies were included in this category of meta-analysis [22, 24–26, 30, 34, 43, 45, 48, 50]. The final pooled meta-analysis showed no statistically significant difference in the rate of LBW among women who were primipara and multipara, OR = 1.2 (95% CI = 0.9, 1.5) (Figure 7).Figure 7
Forest plot displaying the association of being primipara and low birth weight in Ethiopia.


## 3.9. Residence and LBW

From 13 studies included in this category of meta-analysis [22,24–26, 29, 34, 40, 43, 45–49], two studies showed higher LBW risk among babies born from urban resident mothers [34, 40]. But, nine studies showed an increased risk of LBW among rural residents [24–26, 29, 43, 46–49]. Two studies showed no statistically significant difference in the rate of LBW among rural and urban resident mothers [22, 45]. The final pooled meta-analysis showed that babies born from rural mothers were at a higher risk of low birth weight compared to those born from an urban area, OR = 1.75 (95% CI = 1.19, 2.56) (Figure 8).Figure 8
Forest plot displaying the association of rural residence and low birth weight in Ethiopia.


## 3.10. Heterogeneity and Publication Bias

Egger’s test was conducted to assess the publication bias of studies included in this meta-analysis. Accordingly, nonsignificant publication bias was observed in all categories of meta-analysis,p value >0.05. For studies that present with high heterogeneity between studies, the random effect method of analysis was used.


## 3.11. Meta-Regression

The meta-analysis showed evidence of heterogeneity of included studies, and therefore, meta-regression was conducted to assess the source of heterogeneity. However, none of the covariates tested for source of heterogeneity were statistically significant. Therefore, the heterogeneity could be explained by other variables not included in this meta-analysis (Table3).Table 3
Meta-regression analysis of the different study-level covariates explaining possible sources of heterogeneity.
Study characteristicsCoefficientp valuePublication year0.2270.162Sample size<0.0010.578Cohort study design−1.2190.671Addis Ababa city−4.450.595Amhara2.0420.791Oromia1.9380.790SNNPR−3.1570.681Tigray2.1580.779National study6.3440.451


## 4. Discussion

This systematic review and meta-analysis were carried out to assess the pooled prevalence of low birth weight and its determinant factors in Ethiopia. The weight of the newborn at birth is considered as the most important factor related to perinatal and infant morbidity and mortality [52, 53]. Low birth weight babies are almost 20 times more likely to die compared to normal birth weight babies [1].This review found a higher prevalence of low birth weight in Ethiopia. The prevalence was 14.1% (95% CI = 11.2, 17.1). This is almost similar to the prevalence of LBW in sub-Saharan Africa, which ranges from 13% to 15% [1]. A study conducted in Cameroon showed a 13.5% prevalence of LBW [54]. A lower prevalence of LBW (8.7%) was also observed in a study undertaken in Colombia [53]. While a higher prevalence (30.3%) of LBW was found in a study conducted in India [55]. The sociodemographic, economic, nutritional, and healthcare seeking behaviors of pregnant mothers and health service differences could be possible reasons for the higher and lower estimates.A variety of differences in the prevalence of LBW between the different regions in Ethiopia was found. A higher prevalence of LBW (15.4%) was seen in Tigray region, while the lowest (8.66%) was in Addis Ababa, Capital city of Ethiopia. Such disparities could be due to the difference in the sociodemographic, economic, healthcare seeking behavior, and nutritional status of pregnant women in different regions of the country. The subgroup analysis of the prevalence of LBW by publication year showed an increasing trend from 1990 to 2017. The rising prevalence in the LBW could be attributed to the increasing health care seeking behavior and reduced home delivery, which all increased the case detection rate over time in Ethiopia.The finding of this meta-analysis also showed the presence of a statistically significant association between the sex of the newborn and low birth weight, OR 1.5 (1.2, 1.7). Female newborn babies had a 46% higher odd of being low birth weight than male babies. This finding was congruent with the study conducted in Arunachal Pradesh [56]. The higher LBW risk among females than male newborn babies could be due to the difference in chromosomal factors among male and female babies. Term male infants weigh between 150 and 200 g more than females [16].Mothers who did not attend ANC for that pregnancy were 1.7 (OR 1.4, 2.2) times more likely to have low birth weight. Studies conducted in other countries also support this idea [16, 57–60]. Mothers who attended ANC are likely to get health education and counseling about pregnancy, which enables them to avoid modifiable risk factors for low birth weight. For example; studies have shown that prenatal interventions such as prevention of smoking during pregnancy, nutritional education, and prevention and early treatment of medical conditions during pregnancy are responsible for the reduction of low birth weight babies among women who follow antenatal care [60]. However, the effectiveness of prenatal care in reducing pregnancy complications depends on the number of visits and the time the women booked for prenatal care. Therefore, studies showing the effect of frequency of antenatal follow-ups and the birth of the baby are needed.In this meta-analysis, preterm babies were 4.7 (OR 1.5, 14.5) times more likely to be low birth weight compared to term babies. A baby born early has less time in the mother’s uterus to grow and gain weight, and much of a fetus’s weight is increased during the latter part of the mother’s pregnancy [16].Mothers who had pregnancy-induced hypertension were 6.7 times more likely to have low birth weight babies, OR 6.7 (3.5, 12.9). This finding is in line with the studies conducted in Karnataka, India, and Campinas, Brazil [61, 62]. This might be due to the trophoblast invasion into the spiral arteries that supply the placenta is incomplete due to pregnancy-induced hypertension. The reduced uteroplacental blood perfusion leads to intrauterine growth retardation and low birth weight [63].Parity is not associated with low birth weight in this meta-analysis. This could be because the studies included in this analysis have only two categories for parity (primipara and multipara). Previous studies showed that first and four and above births are more likely to be low birth weight compared to second and third births. The reason for this is that the uterus, especially the vascular structures, is not well matured for all purposes during the first pregnancy. The uterine vascular conditions start to decline increasing the risk of low birth weight beginning with the fourth pregnancy [16].Maternal place of residence was associated with low birth weight (OR 1.6 (1.2–2.6)). Mothers living in rural areas had a 75% higher risk of giving low birth weight babies than mothers living in the urban areas. This finding is consistent with the study conducted in Punjab [64]. Rural resident pregnant women are more prone to maternal psychosocial stress, which is implicated in increasing the release of catecholamine and cortisol, and subsequently stimulates the release of corticotrophin-releasing hormone (CRH) through cortisol. The release of CRH has been hypothesized to initiate the onset of labor via a series of biochemical processes, while cortisol has been linked with intrauterine growth restriction and low birth weight [65].Although this study has assessed the effect of selected variables on the occurrence of low birth weight, the factors are not limited to these. Previous studies have also reported additional factors associated with low birth weight. These include poverty, nonuse of antenatal care, low social support and unwanted pregnancy [43], preterm birth, maternal chronic illness and maternal weight below 50 kg [29], and a history of perinatal death and antepartum hemorrhage [22]. Therefore, future review and meta-analysis studies should consider addressing other factors not included in the current study.This review used a comprehensive search strategy to retrieve both published and unpublished studies. Several authors were involved in each step of the meta-analysis. The review followed the PRISMA guideline for meta-analysis. On the other hand, because of the nature of the studies included, parity was dichotomized only into two, which may lead to a lack of association with low birth weight. Therefore, further studies are recommended to identify the effect of parity on low birth weight in Ethiopia. This study included the effect of selected factors on low birth weight. The factors are not limited to those included in this review, and further reviews to show the association of LBW with other sociodemographic, maternal, and newborn characteristics are needed.


## 5. Conclusions

The prevalence of low birth weight was high in Ethiopia, with high variation across the different regions in the country. This requires targeted interventions to regions with a higher prevalence of LBW. This review also showed the association of LBW with several factors. Variables such as sex of the newborn, prenatal care follow-up, pregnancy-induced hypertension, preterm delivery, and residence of the mother were significantly associated with LBW. No statistically significant association was observed in the rate of LBW among primigravida and multigravida mothers. Emphasis should be given to mothers living in rural areas. Community-based health promotion activities on maternal nutrition during pregnancy, antenatal follow-up, prevention, and early treatment of PIH are needed to reduce the high burden of LBW in Ethiopia.



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