Anemia during pregnancy in a Chinese population

Maternal and Neonatal Outcomes of Iron Deficiency Anemia: A Retrospective Cohort Study

INTRODUCTION

Understanding the outcomes of anemia in pregnancy is critical. Since no study has been conducted regarding the maternal and neonatal outcomes of iron-deficiency anemia in Hormozgan province of Iran, this study aims to assess the maternal and neonatal outcomes of iron-deficiency anemia in women who gave birth in Hormozgan province from January 2020 to January 2022.

METHODS

 We retrospectively assessed all singleton pregnant women who gave birth at a tertiary hospital in Bandar Abbas, Hormozgan province, Iran, for two years. We divided all women into iron-deficiency anemic and non-iron-deficiency anemic women. Iron-deficiency anemia was defined as hemoglobin less than 10.5 mg/dl at the time of admission without any other hemoglobinopathy, such as sickle cell anemia or thalassemia. Using electronic patient records, data were extracted from the Iranian Maternal and Neonatal Network (IMaN Net), a valid national system. Since the information of birth under 24 weeks of gestation is not recorded in this system, we excluded all deliveries under 24 weeks of gestation. The outcome measures of the study were demographic factors (age, education, residency place, access to prenatal care, smoking), obstetrical factors (parity, labor induction, fetal presentation, mode of delivery), and maternal and neonatal outcomes (the incidence of preeclampsia, gestational diabetes, placenta abruption, postpartum hemorrhage, maternal need for blood transfusion, maternal need for intensive care unit, preterm birth, low birth weight, intrauterine growth retardation, birth asphyxia, stillbirth, and neonatal intensive care admission). Chi-square tests were used to compare differences between iron-deficiency anemic and non-iron-deficiency anemic women. Logistic regression models were used to assess the effect of iron-deficiency anemia on maternal and neonatal outcomes. The result was presented as odds ratio (OR) or adjusted odds ratio (aOR) after adjusting for covariates and a 95% confidence interval (CI).  Results: The incidence of iron-deficiency anemia was 2.97%. Education and residency were among the demographic factors that differed significantly between groups. Iron-deficiency anemia was more frequent in those with higher education and women who lived in rural areas. In terms of obstetrical factors, method of delivery was the only significantly different factor between groups. Iron-deficiency anemic mothers had substantially more instrumental deliveries than non-iron-deficiency anemic mothers (4.3% vs. 0.8%), while the incidence of cesarean section was lower. Based on logistic regression in terms of maternal and neonatal outcomes, iron-deficiency anemic women had a substantially higher risk of the need for maternal blood transfusion (aOR: 6.54, 95%CI: 4.72-8.15), postpartum hemorrhage (aOR: 1.54, 95%CI: 0.71-2.11), preterm birth (aOR: 0.98, 95%CI: 0.45-1.13), low birth weight (aOR: 1.04, 95%CI: 0.78-2.01), intrauterine growth retardation (aOR: 1.30, 95%CI: 0.99-2.10), and neonatal intensive care admission (aOR: 1.06, 95%CI: p.52-2.72), after adjusting for educational level, residency place, and method of delivery.

CONCLUSIONS

Despite the higher incidence of postpartum hemorrhage and maternal blood transfusion, we found no increase in maternal intensive care unit admission risk. Regarding neonatal outcomes, iron-deficiency anemia was linked to preterm birth, low birth weight, intrauterine growth retardation, and neonatal intensive care admission.

The association between maternal anemia during pregnancy and preterm birth

BACKGROUND & AIMS

Maternal anemia is one of the most serious health problems during pregnancy. The causes of anemia include iron deficiency, parasitic diseases, micronutrient deficiencies, and hereditary hemoglobinopathies. Because the reported association between maternal anemia and preterm labor in different studies is varied depending on the month of pregnancy this study aims to determine this relationship after adjustment for potential confounders.

METHODS

A case-control study was conducted among 801 pregnant women (267 cases and 534 controls) in Sardashat, Iran from October 2012 to October 2013. Hemoglobin (Hb) values were measured for all women participating in the study during the first and second trimesters of pregnancy, and the average Hb values were presented. Statistical analyzes were performed with logistic regression.

RESULTS

The mean age of participants was 26.4 ± 5.25 years for the case group and 27.2 ± 6.51 years for the control group. Preterm birth was associated with maternal anemia during pregnancy [aOR = 2.69 (95% CI; 1.46 to 4.95)] even after adjusting for confounding effects including maternal age, history of abortion [aOR = 2.41 (95% CI; 1.42 to 4.08)], history of preterm birth [aOR = 11.38 (95% CI; 3.48 to 37.22)], obesity (aOR: 3.441; CI95%: 1.18-10.06), parity [aOR = 0.42 (95% CI; 0.25 to 0.69)], preeclampsia/eclampsia [aOR = 6.08 (95% CI; 2.64 to 14)], and GDM [aOR = 4.80 (95% CI; 2.02 to 11.41)]).

CONCLUSION

Early detection and adequate treatment of anemia during pregnancy can help reduce the prevalence of preterm birth.

Maternal low and high hemoglobin concentrations and associations with adverse maternal and infant health outcomes: an updated global systematic review and meta-analysis

BACKGROUND

Growing evidence suggests low and high maternal hemoglobin (Hb) concentrations may have adverse consequences for maternal and child health. There remain questions on specific Hb thresholds to define anemia and high Hb as well as how cutoffs may vary by anemia etiology and timing of assessment.

METHODS

We conducted an updated systematic review (using PubMed and Cochrane Review) on low (< 110 g/L) and high (≥ 130 g/L) maternal Hb concentrations and associations with a range of maternal and infant health outcomes. We examined associations by timing of Hb assessment (preconception; first, second, and third trimesters, as well as at any time point in pregnancy), varying cutoffs used for defining low and high hemoglobin concentrations and performed stratified analyses by iron-deficiency anemia. We conducted meta-analyses to obtain odds ratios (OR) and 95% confidence intervals.

RESULTS

The updated systematic review included 148 studies. Low maternal Hb at any time point in pregnancy was associated with: low birthweight, LBW (OR (95% CI) 1.28 (1.22-1.35)), very low birthweight, VLBW (2.15 (1.47-3.13)), preterm birth, PTB (1.35 (1.29-1.42)), small-for-gestational age, SGA (1.11 (1.02-1.19)), stillbirth 1.43 (1.24-1.65)), perinatal mortality (1.75 (1.28-2.39)), neonatal mortality (1.25 (1.16-1.34), postpartum hemorrhage (1.69 (1.45-1.97)), transfusion (3.68 (2.58-5.26)), pre-eclampsia (1.57 (1.23-2.01)), and prenatal depression (1.44 (1.24-1.68)). For maternal mortality, the OR was higher for Hb < 90 (4.83 (2.17-10.74)) than for Hb < 100 (2.87 (1.08-7.67)). High maternal Hb was associated with: VLBW (1.35 (1.16-1.57)), PTB (1.12 (1.00-1.25)), SGA (1.17 (1.09-1.25)), stillbirth (1.32 (1.09-1.60)), maternal mortality (2.01 (1.12-3.61)), gestational diabetes (1.71 (1.19-2.46)), and pre-eclampsia (1.34 (1.16-1.56)). Stronger associations were noted earlier in pregnancy for low Hb and adverse birth outcomes while the role of timing of high Hb was inconsistent. Lower Hb cutoffs were associated with greater odds of poor outcomes; for high Hb, data were too limited to identify patterns. Information on anemia etiology was limited; relationships did not vary by iron-deficiency anemia.

CONCLUSION

Both low and high maternal Hb concentrations during pregnancy are strong predictors of adverse maternal and infant health outcomes. Additional research is needed to establish healthy reference ranges and design effective interventions to optimize maternal Hb during pregnancy.

Effect of Intrapartum Maternal Hemoglobin on Mode of Delivery and Short-Term Neonatal Outcome: A Systematic Review

Importance

Maternal anemia in pregnancy is a common condition worldwide and is considered a risk factor for adverse neonatal and maternal outcome. Also high hemoglobin (Hb) levels are associated with adverse pregnancy outcomes. However, studies regarding the influence of intrapartum maternal Hb on mode of delivery and short-term neonatal outcome are limited and contradicting.

Objective

The aim of this study was to provide an overview of current evidence regarding associations between intrapartum maternal Hb levels and mode of delivery and short-term neonatal outcome. In addition, we propose directions for future research.

Evidence Acquisition

We systematically searched the electronic PubMed, EMBASE, and Cochrane databases for studies on maternal Hb levels and mode of delivery maternal and short-term neonatal outcome until January 2021. Eligible articles and their references were independently reviewed by 2 authors. Assessment was based on methodological quality and study results.

Results

We included 14 studies that evaluated the level of maternal pH in relation to clinical outcome, 6 studies on mode of delivery, 10 studies on Apgar score, 1 study on fetal distress, 2 studies on neonatal intensive care unit admission, 1 study on umbilical cord pH, and 5 studies on perinatal mortality.

Conclusions and Relevance

We found a trend toward an increased risk of cesarean delivery in anemic woman. Concerning the short-term neonatal outcomes, the evidence is conflicting, and included studies are too heterogenic to compare. Furthermore, various studies indicated a relation between high Hb levels and increased perinatal mortality. Therefore, we especially recommend attention to elevated Hb levels.

Target Audience

Obstetricians and gynecologists, family physicians.

Learning Objectives

After completing this activity, the learner should be better able to describe how Hb levels affect mode of delivery and short-term neonatal outcome, and identify abnormal Hb levels and propose appropriate treatment and monitoring recommendations.

The Associations of Maternal Hemoglobin Concentration in Different Time Points and Its Changes during Pregnancy with Birth Weight Outcomes

Maternal hemoglobin (Hb) is related to nutritional status, which affects neonatal birth weight. However, it is very common for maternal Hb to fluctuate during pregnancy. To evaluate the associations of maternal Hb in different time points and its changes during pregnancy with neonatal birth weight, small for gestational age (SGA)/low birth weight (LBW) and large for gestational age (LGA)/macrosomia, we conducted this study by using data from the Electronic Medical Record System (EMRS) database of Zhoushan Maternal and Child Care Hospital in Zhejiang province, China. The pregnancy was divided into five periods: first, early-second, mediate-second, late-second, early-third and late-third trimesters; we further calculated the maternal Hb changes during pregnancy. Overall, the socio-demographic characteristics, health-related information and childbirth-related information of 24,183 mother−infant pairs were obtained. The average Hb concentration during the different periods were 123.95 ± 10.14, 117.95 ± 9.84, 114.31 ± 9.03, 113.26 ± 8.82, 113.29 ± 8.68 and 115.01 ± 8.85 g/L, respectively. Significant dose−response relationships between maternal Hb and birth weight were observed in the first, late-second and later trimesters (p non-linear < 0.05). Maternal Hb < 100 g/L was related to a high risk of LGA/macrosomia in the late-second (OR: 1.47, 95% CI: 1.18, 1.83) and later trimesters; additionally, high maternal Hb (>140 g/L) increased the risk of SGA/LBW in the first (OR: 1.26, 95% CI: 1.01, 1.57) and late-third trimesters (OR: 1.96, 95% CI: 1.20, 3.18). In addition, the increase in maternal Hb from the late-second to late-third trimesters had a positive correlation with SGA/LBW. In conclusion, maternal Hb markedly fluctuated during pregnancy; the negative dose−response association of maternal Hb in the late-second and third trimesters, and Hb change during pregnancy with neonatal birth weight outcomes were observed, respectively. Furthermore, the phenomenon of high Hb in the first trimester and after the late-second trimester and the increase of maternal Hb from the late-second to late-third trimesters more significantly increasing the risk of SGA/LBW should especially be given more attention. Its biological mechanism needs to be further explored.

Global Prevalence of Anemia in Pregnant Women: A Comprehensive Systematic Review and Meta-Analysis

BACKGROUND

Anemia is one of the most critical health conditions affecting people worldwide. The disease is silent, with a slow progression and a few physical symptoms. Anemia during pregnancy carries the risk of premature birth, low birth weight, and fetus malformations and can impose additional costs on society and families. Therefore, the aim of this study is to conduct a systematic review and meta-analysis on the prevalence of anemia in pregnant women worldwide.

METHODS

In this work, we have conducted a systematic review and meta-analysis of the studies that have examined the prevalence of anemia in pregnant women globally. The Google Scholar, Cochrane, ScienceDirect, Medline (PubMed), and Web of Science (WoS) databases were searched for articles published between 1991 and 2021. The search keywords were anemia, pregnancy, prevalence, and meta-analysis. In order to analyze the eligible studies, the stochastic effects model was used, and the heterogeneity of the studies was examined using the I² index. Data analysis was performed within the Comprehensive Meta-Analysis software (Version 2).

RESULTS

The search resulted in 338 deduplicated studies, of which 52 studies with a total sample size of 1,244,747 people were included in this review. According to the results of the meta-analysis, the overall prevalence of anemia in pregnant women is 36.8% (95% confidence interval: 31.5-42.4%). The highest prevalence of anemia is mild at 70.8 (95% CI 58.1-81) and highest in the third trimester of pregnancy with the prevalence of 48.8 (95% CI 38.7-58.9), while the highest prevalence of anemia in pregnant women was in Africa with the prevalence of 41.7 (95% CI 32.3-49.4).

CONCLUSION

The results of this study show a high prevalence of anemia among pregnant women worldwide, and the highest of this prevalence is mild anemia. The prevalence of anemia in the third trimester was higher than in the first and second trimesters. Anemia in pregnant women in developing countries is significantly higher than in developed countries due to pregnancy's economic, sociological, and health factors.

Association of Maternal Longitudinal Hemoglobin with Small for Gestational Age during Pregnancy: A Prospective Cohort Study

Background: Few studies have investigated the association of maternal longitudinal hemoglobin (Hb) with small for gestational age during pregnancy. The current study examined the associations of maternal Hb concentrations and Hb changes throughout the middle and late stages of pregnancy with small for gestational age (SGA) in a large prospective cohort study. Methods: This was a prospective cohort study, which enrolled pregnant women at 8−16 weeks of gestation and followed up regularly. Maternal Hb concentrations were measured at the middle (14−27 weeks) and late (28−42 weeks) stages of pregnancy, and the Hb change from the middle to late stage of pregnancy was assessed. The Log-Poisson regression model was used to identify the association of maternal Hb with SGA, including the implications of Hb during specific pregnancy periods and Hb change across the middle to late stages of pregnancy. Of the total 3233 singleton live births, 208 (6.4%) were SGA. After adjusting for potential confounders, compared with Hb 110−119 g/L, Hb ≥ 130 g/L at late pregnancy was significantly associated with a higher risk of SGA (adjusted RR: 2.16; 95% CI: 1.49, 3.13). When Hb changes from the middle to late stages of pregnancy were classified by tertiles, the greatest change in the Hb group (<−6.0 g/L) was significantly associated with a lower risk of SGA (adjusted RR: 0.56; 95% CI: 0.37, 0.85) compared with the intermediate group (−6.0~1.9 g/L). In conclusion, for women at low risk of iron deficiency, both higher Hb concentrations in late pregnancy and less Hb reduction during pregnancy were associated with an increased risk of SGA.

Maternal anaemia and risk of adverse obstetric and neonatal outcomes in South Asian countries: A systematic review and meta-analysis

Background

The occurrence of maternal anaemia is common in South Asian countries which increase the risk of adverse maternal obstetric and birth outcomes. This may adversely affect the achievement of the Sustainable Development Goals’ (SDG) targets of reducing maternal and under-five deaths by 2030.

Objectives

To summarize the evidence on the association of maternal anaemia with adverse birth and maternal obstetric outcomes.

Methods

We adopted the PRISMA consensus statement. PubMed, CINAHL and Web of Science databases were searched on February 20, 2020. A total of 38 studies was included, of which 25 articles were included in the quantitative synthesis and meta-analysis.

Results

Maternal anaemia was associated with a significantly higher risk of low birth weight (OR, 1.90; 95% CI, 1.06-2.60, p ​< ​0.05), preterm birth (OR, 1.96; 95% CI, 1.20-2.41, p ​< ​0.05) and perinatal mortality (OR, 2.90; 1.97-3.78, p ​< ​0.05). Non-significant associations were seen with neonatal mortality (OR, 1.80; 95% CI, 0.90-27.77, p ​= ​0.7), miscarriage (OR, 1.68; 95% CI, 0.48-3.20, p ​= ​0.08), preeclampsia (OR, 2.66; 95% CI, 0.61-11.52, p ​= ​0.6) and caesarean delivery (OR, 1.18; 95% CI, 0.36-2.80, p ​= ​0.07).

Conclusion

Maternal anaemia increases the risk of low birth weight, preterm birth and perinatal mortality. Improving maternal nutritional status and iron supplementation during pregnancy are important for reducing these adverse outcomes.

Iron Deficiency and Iron Deficiency Anemia: Implications and Impact in Pregnancy, Fetal Development, and Early Childhood Parameters

A normal pregnancy consumes 500–800 mg of iron from the mother. Premenopausal women have a high incidence of marginal iron stores or iron deficiency (ID), with or without anemia, particularly in the less developed world. Although pregnancy is associated with a “physiologic” anemia largely related to maternal volume expansion; it is paradoxically associated with an increase in erythrocyte production and erythrocyte mass/kg. ID is a limiting factor for this erythrocyte mass expansion and can contribute to adverse pregnancy outcomes. This review summarizes erythrocyte and iron balance observed in pregnancy; its implications and impact on mother and child; and provides an overview of approaches to the recognition of ID in pregnancy and its management, including clinically relevant questions for further investigation.

Relationship between anaemia during pregnancy and preterm delivery

The purpose of this study was to analyse the relationship between preterm delivery and maternal anaemia. This retrospective cohort study was completed with 483 women; 294 of them had a normal delivery and 189 had a preterm delivery. The haemoglobin (Hb) values of all the women participating in the study were measured in the first and second trimesters, and the average Hb values were calculated. The pregnant women participating in the study were divided into three groups, according to their Hb level: those with Hb level <10 g/dl, those with Hb level between 10 and 11 g/dl and those with Hb level >11 g/dl. In crude analysis, women with low Hb levels had an increased rate of preterm delivery (odds ratio, 2.42; 95% CI, 1.07-5.49). Our study provides data that low Hb level is effective in preterm delivery. Impact statement What is already known on this subject? Serum Hb levels have inconsistent associations with a risk of preterm delivery. What the results of this study add? Compared with term delivery Hb levels are lower in preterm delivery. It is necessary to take into account the Hb levels of both the first and second trimester of the pregnancy when describing the pregnancy anaemia. What the implications are of these findings for clinical practice and/or further research? Given these results, physicians should take into account anaemia in pregnancy when considering the risk of a preterm delivery.

Maternal hemoglobin concentrations across pregnancy and maternal and child health: a systematic review and meta-analysis

Maternal anemia is a well‐recognized global health problem; however, there remain questions on specific hemoglobin (Hb) thresholds that predict health risk or protection for mother and child. We conducted a systematic review and meta‐analysis to examine the associations of maternal Hb concentrations with a range of maternal and infant health outcomes, accounting for the timing of measurement (preconception, and first, second, and third trimesters), etiology of anemia, and cutoff category. The systematic review included 272 studies and the meta‐analysis included 95 studies. Low maternal Hb (<110 g/L) was associated with poor birth outcomes (low birth weight, preterm birth, small‐for‐gestational‐age (SGA), stillbirth, and perinatal and neonatal mortality) and adverse maternal outcomes (postpartum hemorrhage, preeclampsia, and blood transfusion). High maternal Hb (>130 g/L) was associated with increased odds of SGA, stillbirth, preeclampsia, and gestational diabetes. Relationships varied by the timing of measurement and cutoff category (stronger associations with lower cutoffs); limited data were available on anemia etiology. There were insufficient data for other maternal outcomes and long‐term child health outcomes. Current data are insufficient for determining if revisions to current Hb cutoffs are required. Pooled high‐quality individual‐level data analyses, as well as prospective cohort studies, would be valuable to inform the reevaluation of Hb cutoffs.

Socio-economic determinants of anemia in pregnancy in North Shoa Zone, Ethiopia

BACKGROUND

Globally, anemia in pregnancy increases maternal, fetal and neonatal mortality and morbidity. According to 2011 Ethiopian Demographic and Health Survey, 22% of pregnant women in Ethiopia were reported to be anemic. However, since the Ethiopian population is diverse with regard to culture, religion and other characteristics, this evidence may not represent the condition in our study area. So, we aimed to determine the prevalence of anemia and its associated factors among women receiving Antenatal Care (ANC) in Debre Berhan Town Hospitals and Clinics.

METHODS

We conducted an institution based cross sectional study among women receiving ANC at hospitals and clinics in Debre Berhan Town, Ethiopia from September to November, 2013. Antenatal care providers in the respective health facilities collected the data by interview and observation using closed and open-ended questions. We computed frequencies and percentages to describe the data. We performed bivariate and multivariable binary logistic regression analyses to identify factors associated with anemia in pregnancy. STATA version 12 was used to carry out the analyses.

RESULTS

A total of 295 participants completed the study, with a response rate of 89%. This study demonstrated a 10% prevalence of anemia out of which 64.3%, 32% and 4% of the respondents were with mild, moderate and severe anemia respectively. Anemia was statistically significantly associated with education and occupation.

CONCLUSION

The prevalence of anemia in our study area is lower than previous studies' findings. Literacy and job status of the women were predictors of anemia in pregnancy. Since this study was conducted on women who had an opportunity to visit health facilities, it is more valuable to conduct community based research to better understand the problem in the study area and thus propose future deliverable.

Maternal Anemia and Low Birth Weight: A Systematic Review and Meta-Analysis

Objective: To systematically analyze the relationship between maternal anemia and low birth weight. Methods: A search of studies was conducted in the main databases (Medline, Embase, Scopus, Web of Science, SciELO, and Lilacs), the gray literature, and the reference lists of selected articles. Cohort and case-control studies that met the eligibility criteria were included in the review. There was no limitation on the language or date of publication. Article selection and data extraction were performed by two independent reviewers. Meta-analyses with random effects, subgroup analyses and meta-regressions were performed. Publication bias was measured using Egger regression and visual funnel plot inspection. Results: A total of 7243 articles were found, of which 71 comprised the systematic review and 68 were included in the meta-analyses. Maternal anemia was associated with low birth weight with an adjusted OR: 1.23 (95% CI: 1.06–1.43) and I²: 58%. The meta-regressions confirmed that the sample size and the methodological quality may partially explain the statistical heterogeneity. Conclusions: Maternal anemia was considered a risk factor for low birth weight.

Maternal Anemia and Low Birth Weight: A Systematic Review and Meta-Analysis

OBJECTIVE

To systematically analyze the relationship between maternal anemia and low birth weight.

METHODS

A search of studies was conducted in the main databases (Medline, Embase, Scopus, Web of Science, SciELO, and Lilacs), the gray literature, and the reference lists of selected articles. Cohort and case-control studies that met the eligibility criteria were included in the review. There was no limitation on the language or date of publication. Article selection and data extraction were performed by two independent reviewers. Meta-analyses with random effects, subgroup analyses and meta-regressions were performed. Publication bias was measured using Egger regression and visual funnel plot inspection.

RESULTS

A total of 7243 articles were found, of which 71 comprised the systematic review and 68 were included in the meta-analyses. Maternal anemia was associated with low birth weight with an adjusted OR: 1.23 (95% CI: 1.06⁻1.43) and I²: 58%. The meta-regressions confirmed that the sample size and the methodological quality may partially explain the statistical heterogeneity.

CONCLUSIONS

Maternal anemia was considered a risk factor for low birth weight.

Maternal haemoglobin concentration and risk of preterm birth in a Chinese population

The aim was to examine the relationship between maternal haemoglobin (Hb) concentrations and risk of preterm birth by secondary analysis of data from a randomised controlled trial. This analysis included 10,430 women who were at least 20 years old and no more than 20 weeks of gestation. Results revealed neither first- nor second-trimester Hb concentrations were associated with the risk of preterm births. However, the risk of preterm birth increased when the Hb level was low (<130 g/L) in the first but high (≥130 g/L) in the second trimester, regardless of supplement type (iron-containing: AOR: 2.26, 95% CI: 1.37-3.73; non-iron-containing: AOR: 2.16, 95% CI: 1.11-4.21). In conclusion, maternal Hb concentrations were not associated with the risk of preterm birth. A low-Hb level in the first trimester but coupled with a high Hb level in the second was associated with an elevated risk of preterm birth. Impact statement What is already known on this subject: The relationship between maternal Hb concentration and preterm birth remains inconclusive. Some studies have shown an association between a low- or a high-Hb level and an increased risk of preterm birth. Others have not found such an association. Yet others have shown a U-shaped relationship. What do the results of this study add: Overall, maternal Hb concentrations in first or second trimester were not statistically associated with the risk of preterm birth. However, women with a low Hb concentration in the first trimester together with a high Hb concentration in the second trimester had an increased risk of preterm birth, compared to women who had a higher Hb concentration in the first trimester that remained similar during the second trimester. What are the implications are of these findings for clinical practice and/or further research: Our finding helps identify mothers who are at risk of having a preterm delivery. Investigating the underlying clinical causes of the unfavourable change in Hb levels and close follow-up to these women may help improve birth outcomes.

Hemoglobin concentration and pregnancy outcomes: a systematic review and meta-analysis

Objective. To conduct a systematic review and meta-analysis of hemoglobin effect on the pregnancy outcomes. Methods. We searched MEDLINE and SCOPUS from January 1, 1990 to April 10, 2011. Observational studies addressing association between hemoglobin and adverse pregnancy outcomes were selected. Two reviewers independently extracted data. A mixed logistic regression was applied to assess the effects of hemoglobin on preterm birth, low birth weight, and small for gestational age. Results. Seventeen studies were included in poolings. Hemoglobin below 11 g/dL was, respectively, 1.10 (95% CI: 1.02–1.19), 1.17 (95% CI: 1.03–1.32), and 1.14 (95% CI: 1.05–1.24) times higher risk of preterm birth, low birth weight, and small for gestational age than normal hemoglobin in the first trimester. In the third trimester, hemoglobin below 11 g/dL was 1.30 (95% CI: 1.08–1.58) times higher risk of low birth weight. Hemoglobin above 14 g/dL in third trimester decreased the risk of preterm term with ORs of 0.50 (95% CI: 0.26–0.97), but it might be affected by publication bias. Conclusions. Our review suggests that hemoglobin below 11 g/dl increases the risk of preterm birth, low birth weight, and small gestational age in the first trimester and the risk of low birth weight in the third trimester.

Anaemia, prenatal iron use, and risk of adverse pregnancy outcomes: systematic review and meta-analysis

OBJECTIVES

To summarise evidence on the associations of maternal anaemia and prenatal iron use with maternal haematological and adverse pregnancy outcomes; and to evaluate potential exposure-response relations of dose of iron, duration of use, and haemoglobin concentration in prenatal period with pregnancy outcomes.

DESIGN

Systematic review and meta-analysis

DATA SOURCES

Searches of PubMed and Embase for studies published up to May 2012 and references of review articles.

STUDY SELECTION CRITERIA

Randomised trials of prenatal iron use and prospective cohort studies of prenatal anaemia; cross sectional and case-control studies were excluded.

RESULTS

48 randomised trials (17 793 women) and 44 cohort studies (1 851 682 women) were included. Iron use increased maternal mean haemoglobin concentration by 4.59 (95% confidence interval 3.72 to 5.46) g/L compared with controls and significantly reduced the risk of anaemia (relative risk 0.50, 0.42 to 0.59), iron deficiency (0.59, 0.46 to 0.79), iron deficiency anaemia (0.40, 0.26 to 0.60), and low birth weight (0.81, 0.71 to 0.93). The effect of iron on preterm birth was not significant (relative risk 0.84, 0.68 to 1.03). Analysis of cohort studies showed a significantly higher risk of low birth weight (adjusted odds ratio 1.29, 1.09 to 1.53) and preterm birth (1.21, 1.13 to 1.30) with anaemia in the first or second trimester. Exposure-response analysis indicated that for every 10 mg increase in iron dose/day, up to 66 mg/day, the relative risk of maternal anaemia was 0.88 (0.84 to 0.92) (P for linear trend<0.001). Birth weight increased by 15.1 (6.0 to 24.2) g (P for linear trend=0.005) and risk of low birth weight decreased by 3% (relative risk 0.97, 0.95 to 0.98) for every 10 mg increase in dose/day (P for linear trend<0.001). Duration of use was not significantly associated with the outcomes after adjustment for dose. Furthermore, for each 1 g/L increase in mean haemoglobin, birth weight increased by 14.0 (6.8 to 21.8) g (P for linear trend=0.002); however, mean haemoglobin was not associated with the risk of low birth weight and preterm birth. No evidence of a significant effect on duration of gestation, small for gestational age births, and birth length was noted.

CONCLUSIONS

Daily prenatal use of iron substantially improved birth weight in a linear dose-response fashion, probably leading to a reduction in risk of low birth weight. An improvement in prenatal mean haemoglobin concentration linearly increased birth weight.

Anemia before pregnancy and risk of preterm birth, low birth weight and small-for-gestational-age birth in Korean women

BACKGROUND/OBJECTIVES

Maternal prepregnancy hemoglobin concentration has rarely been explored as a risk of poor birth outcomes. This study examined whether women with anemia before pregnancy would be at higher risk of preterm birth, low birth weight (LBW) and small-for-gestational-age (SGA) birth.

SUBJECTS/METHODS

This retrospective cohort study was conducted on 70,895 Korean women who delivered a singleton in 1999, with their prepregnancy hemoglobin concentration measured at health examinations in 1997-1999. A logistic model was used to adjust for confounding variables and calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

In adjusted analysis, moderate-to-severe anemia (hemoglobin <100 g/l) before pregnancy was associated with preterm birth (OR, 1.53; 95% CI, 1.05-2.23; P=0.027), LBW (OR, 1.81; 95% CI, 1.24-2.64; P=0.002) and SGA (OR, 1.71; 95% CI, 1.35-2.17; P<0.001) when compared with prepregnancy hemoglobin of 120-149 g/l. Mild anemia (hemoglobin of 100-119 g/l) was also associated with LBW (OR, 1.21; 95% CI, 1.06-1.39; P=0.005) and SGA (OR, 1.15; 95% CI, 1.06-1.25; P=0.001). The risk of preterm birth, LBW and SGA across 11 prepregnancy hemoglobin groups depended on the severity of anemia (P for trend=0.042, 0.019, and 0.001, respectively). A high hemoglobin concentration (≥150 g/l), however, was not associated with adverse birth outcomes.

CONCLUSIONS

Anemia, not high hemoglobin concentration, before pregnancy was associated with an elevated risk of preterm birth, LBW and SGA, and the risk increased with the severity of anemia in Korean women.

Maternal anemia in pregnancy: assessing the effect of routine preventive measures in a malaria-endemic area

We investigated the effectiveness of routine preventive measures for anemia in Beninese pregnant women during pregnancy. Anemia (hemoglobin < 110 g/L) was common: 68.3% at first antenatal visit (ANV1), 64.7% at second antenatal visit (ANV2), and 40.6% at delivery. Parasitic infections and nutritional deficiencies were the most preventable causes. After intermittent preventive treatment (IPTp) and antihelminthic treatments, malaria prevalence decreased from 15.1% (ANV1) to 4.0% (ANV2) and increased again to 9.6% at delivery. Helminth infections dropped from 11.1% (ANV1) to 7.2% (ANV2) and 2.4% at delivery. Malaria was associated with lower mean hemoglobin on ANV1 and delivery, and iron deficiency was associated with lower mean hemoglobin on ANV1 and ANV2. IPTp and antihelminthic treatments were efficacious to clear parasitic infections and improve hematologic status, whereas the effectiveness of daily iron and folic acid supplements to correct iron and folate deficiencies and decrease anemia was less marked, possibly because of lack of compliance.

Maternal anemia at first antenatal visit: prevalence and risk factors in a malaria-endemic area in Benin

The risk factors for maternal anemia (hemoglobin level less than 110 g/L) were studied in human immunodeficiency virus-negative pregnant women in Benin at the time of first antenatal visit and prior to any prevention. Data for the first 1,005 pregnant women included in a multicentre randomized controlled trial were analyzed. Anemia was common (68.3%), and malaria and helminth infestations were prevalent in 15.2% and 11.1% of the women. A total of 33.3%, 31.3% and 3.6% of the women were iron, folic acid and vitamin B12 deficient, respectively. These parasitic infections and nutrient deficiencies were associated with a high risk of anemia. Twenty-one percent, 15%, 12%, 11% and 7% of anemia were attributable to malnutrition, malaria, iron, folic acid deficiencies, and helminth infestations, respectively. Most anemia was caused by factors that could be prevented by available tools, stressing the need to reinforce their implementation and to evaluate their effectiveness throughout the course of the pregnancy.

Anaemia during pregnancy: impact on birth outcome and infant haemoglobin level during the first 18 months of life

To determine the effect of maternal anaemia on pregnancy outcome and describe its impact on infant haemoglobin level in the first 18 months of life, we conducted a prospective study of 617 pregnant women and their children in Benin. Prevalence of maternal anaemia at delivery was 39.5%, and 61.1% of newborns were anaemic at birth. Maternal anaemia was not associated with low birth weight [OR = 1.2 (0.6-2.2)] or preterm birth [OR = 1.3 (0.7-2.4)], whereas the newborn's anaemia was related to maternal anaemia [OR = 1.8 (1.2-2.5)]. There was no association between an infant's haemoglobin level until 18 months and maternal anaemia. However, malaria attacks during follow-up, male gender and sickle cell trait were all associated with a lower infant haemoglobin level until 18 months, whereas good infant feeding practices and a polygamous family were positively associated with a higher haemoglobin level during the first 18 months of life.

Maternal anemia in Benin: prevalence, risk factors, and association with low birth weight

We studied the prevalence of anemia during pregnancy and its relationship with low birth weight (LBW; birth weight < 2,500 g) in Benin. We analyzed 1,508 observations from a randomized controlled trial conducted from 2005 to 2008 showing equivalence on the risk of LBW between two drugs for Intermittent Preventive Treatment of malaria during pregnancy (IPTp). Despite IPTp, helminth prophylaxis, and iron and folic acid supplementations, the proportions of women with severe anemia (hemoglobin [Hb] concentration < 80 g/L) and anemia (Hb < 110 g/L) were high throughout pregnancy: 3.9% and 64.7% during the second and 3.7% and 64.1% during the third trimester, but 2.5% and 39.6% at the onset of labor, respectively. Compared with women without anemia (Hb ≥ 110 g/L) during the third trimester, women with severe anemia (Hb < 80 g/L) were at higher risk of LBW after adjustment for potential confounding factors (prevalence ratio [PR] = 2.8; 95% confidence interval [1.4-5.6]).

The impact of maternal anemia on perinatal mortality: a population-based, prospective cohort study in China

PURPOSE

To evaluate whether anemia during pregnancy is associated with increased risk of stillbirth and neonatal death.

METHODS

A prospective cohort study, using data from a population-based pregnancy-monitoring system in 13 counties in East China (1993-1996) was conducted. Singleton live births (n=163,313) and stillbirths (n=1,354) delivered at 20 to 44 weeks to women with one or more hemoglobin measures during pregnancy were included. Stillbirth and neonatal mortality rates by anemia status in each trimester were estimated. Multivariable Cox proportional hazards regression models were used to evaluate the association between hemoglobin levels and mortality risk.

RESULTS

The stillbirth rates were 6.2 and 9.2 per 1,000 births in women with and without anemia (hemoglobin < 10 g/dL), respectively. The protective effect of anemia was mainly in the third trimester. Hemoglobin of 9 g/dL in the third trimester was associated with reduced risk (hazard ratio [HR], 0.8; 95% confidence interval [CI], 0.7-0.97). Maternal anemia was not associated with neonatal mortality.

CONCLUSIONS

Although maternal anemia was not associated with increased risk of mortality in the neonatal period, women with anemia during the third trimester had lower risk of stillbirth.

Anaemia and pregnancy outcomes in a South African rural population

The purpose of this study was to evaluate whether the booking haemoglobin (Hb) did affect the mode of delivery or the birth weight. A total of 3,214 booking Hb was available from 1,628 primiparas and 1,586 multiparas. A total of 507 had a caesarean section and 2,707 a spontaneous vaginal delivery (SVD). Moderate and severe anaemia were defined, respectively as an Hb of <10 and <8 g/dl. There were only 112 women with recorded evidence of iron and folate supplementation. The overall prevalence of anaemia was 19.7%. Multigravidas with SVD had a 22.5% prevalence of booking Hb <10 vs 14.2% in primigravidas (p < 0.0001). The prevalence of severe anaemia was similar for all subgroups. Simple regression analysis showed no significant correlation between the booking Hb and pregnancy outcome in terms of birth weight or mode of delivery. However, booking visit anaemia could predispose to caesarean delivery. Documented iron and folate supplementation did not appear to result in different pregnancy outcomes.

Prevalence and risk factors for anaemia in pregnant women: a population-based prospective cohort study in China

Maternal anaemia is a common pregnancy complication in developing countries; however, its epidemiology remains largely unexplored in China. This study was designed to explore the epidemiology and risk factors of anaemia during pregnancy. A prospective cohort study was conducted, using data from a population-based pregnancy-monitoring system in 13 counties in East China (1993-96). Women who delivered singleton infants at 20-44 weeks with at least one haemoglobin assessment during pregnancy were included (n = 164 667). The prevalence of anaemia (haemoglobin < 10 g/dL) during pregnancy as well as in each trimester was estimated. Multivariable log-binomial regression models were used to evaluate risk factors. The overall prevalence of anaemia in pregnancy was 32.6%, with substantial variations across trimesters (11.2%, 20.1% and 26.2% in the 1st, 2nd and 3rd trimesters respectively). Risk factors for anaemia included older maternal age, education below junior high school (prevalence rate ratio [RR] 1.10, 95% confidence interval [CI] 1.08, 1.12), farming occupation (1.05, 95% CI 1.03, 1.06), and mild pregnancy-induced hypertension (PIH) (RR 1.09, 95% CI 1.05, 1.13) and severe PIH (RR 1.13, 95% CI 1.06, 1.19). Peri-conception folic acid use was associated with a reduced risk for anaemia in the 1st trimester (RR 0.75, 95% CI 0.72, 0.78). Initiating prenatal care after the 1st trimester was associated with increased risk of anaemia in the 2nd and 3rd trimesters. Our study found anaemia during pregnancy is highly prevalent in this indigenous Chinese population. The risk increases with the severity of hypertensive disorders. Folic acid supplementation during the peri-conception period is associated with reduced risk of 1st trimester anaemia.

Maternal anaemia as an indicator for monitoring malaria control in pregnancy in sub-Saharan Africa

DESIGN

Malarial anaemia is a major problem in many developing countries and often occurs more frequently in first pregnancies, as primigravidae are more susceptible to Plasmodium falciparum malaria and are at excess risk of malarial anaemia.

OBJECTIVE AND METHODS

To analyse the excess risk of anaemia in primigravidae as a potential indicator of malaria control and exposure in pregnant women living in sub-Saharan Africa. The sensitivity, specificity and predictive values for anaemia in first compared with later pregnancies are calculated for 27 studies from malarious and 7 studies from nonmalarious areas.

SETTING

Surveys of pregnancy anaemia reported for highly malarious and nonmalarious areas.

RESULTS

In malarious areas, the weighted odds ratio for excess anaemia (haemoglobin [Hb] <11 g/dl) in primigravidae compared with multigravidae for all studies was 1.34 (95% CI 1.14-1.58). At an Hb cutoff below 8 g/dl, the weighted odds ratio was 1.79 (95% CI 1.52-2.10). In nonmalarious areas, there was no increased risk of anaemia in primigravidae with Hb below 11 g/dl (OR 0.80; 95% CI 0.63-1.90) or below 8 g/dl (OR 0.82, 95% CI 0.51-1.28).

CONCLUSIONS

In view of the consistency of results across highly malarious areas compared with nonmalarious areas, maternal anaemia has the potential to be used for surveillance of malaria control in pregnancy. Based on the analysis, an anaemia nomogram is developed for use as a surveillance indicator in malarious areas in sub-Saharan Africa.

Low first-trimester hemoglobin and low birth weight, preterm birth and small for gestational age newborns

OBJECTIVE

To examine the relationship between first-trimester hemoglobin (Hb) concentration and risk of low birth weight (LBW), preterm birth and small for gestational age (SGA).

METHODS

Data were obtained from a population-based prenatal care program in China. A total of 88,149 women who delivered during 1995-2000 and had their Hb measured in the first trimester were selected as study subjects.

RESULTS

The prevalence of anemia (Hb<110 g/L) was 22.1% in the first trimester. The risk of LBW, preterm birth and SGA was increased steadily with the decrease of first-trimester Hb concentration. After controlling for confounding factors, women with Hb 80-99 g/L had significantly higher risk for LBW (OR=1.44, 95% CI 1.17-1.78), preterm birth (OR=1.34, 95% CI 1.16-1.55) and SGA (OR=1.13, 95% CI 0.98-1.31) than women with Hb 100-119 g/L. No elevated risk was noted for women with Hb> or =120 g/L.

CONCLUSION

Low first-trimester Hb concentration increases the risk of LBW, preterm birth and SGA.

Risk of stillbirth in relation to maternal haemoglobin concentration during pregnancy

The authors determined the association between maternal haemoglobin concentration measured at <28 weeks' gestation and late fetal death at >or=28 weeks' gestation (stillbirth). Data were derived from the National Maternal and Infant Health Survey--a nationally representative survey of US deliveries in 1988. Analysis was restricted to women with a singleton live birth (n = 4,199) or a stillbirth (n = 1,375) for whom maternal prenatal care, haemoglobin, smoking status and gestational age data were available. Haemoglobin concentrations during first and second trimesters, respectively, were classified as mild (10.0 to <11.0 and 9.5 to <10.5 g dL(-1)) or moderate (9.0 to <10.0 and 8.5 to <9.5 g dL(-1)) anaemia, or high haemoglobin (>or=14.6 g dL(-1) in either trimester). Hazard ratios (HR) and 95% confidence intervals (CI) for stillbirth were derived from discrete proportional hazards regression models after adjusting for confounders. Stillbirth was not associated with mild anaemia or high haemoglobin in either the first or second trimester of pregnancy. Moderate anaemia measured before 28 weeks' gestation was significantly associated with an increased risk of stillbirth among non-black women (adjusted HR: 4.4; 95% CI: 1.02, 19.01). Moderate anaemia was not associated with stillbirths among black women. Further investigation regarding causal mechanisms for this association is warranted.

Obstetric impact of anaemia in pregnant women in United Arab Emirates

Our objective was to determine the effect of anaemia during pregnancy on maternal and perinatal outcome. A retrospective case-control study was conduced on 100 anaemic (haemoglobin level < 11g/dl) and 100 non-anaemic, pregnant women with singleton pregnancies who received antenatal care and delivered vaginally in our hospital. The maternal characteristics of both groups were not different. The causes of anaemia were iron deficiency (91%), beta-thalassaemia trait (8%) and folate deficiency (1%). There was no significant difference in the mean gestational age at delivery (38.9 +/- 2.0 vs 39.6 +/- 1.6 weeks), 5-minute Apgar score (7.8 +/- 0.8 vs 7.9 +/- 0.1) and birth weight (3,150 +/- 530 vs 3,230 +/- 430 g) between both groups. Post-partum haemorrhage (3%), pre-term delivery (4%) and fetal growth restriction (6%) were more frequent in anaemic women but the difference was not significant. Anaemia, therefore, had no significant obstetric adverse effects in our pregnant hospital-population.

[Severe maternal anemia and pregnancy outcome]

OBJECTIVES

The aim of this study was to determine the effects of severe antenatal maternal anemia on pregnancy outcome.

MATERIAL

and methods. A retrospective study comparing 2 groups of pregnant women: 111 (pregnant women) with anemia (Hb < 8 g/dl), 111 non- anemic pregnant women (Hb >10 g/dl). Clinical and biological characteristics for both groups were compared. Data on the newborn babies were collected.

RESULTS

In the anemic group: iron deficiency was the most common cause of anemia (92.7%). There was no significant difference between the 2 groups with respect to age or parity. Maternal anemia was found to be significantly associated with more frequent preterm birth (29.2% vs 9.2%) and increased low birth weight (2933 g vs 3159 g).

DISCUSSION

The literature is not conclusive on the influence of anemia in pregnant women. More frequent preterm birth and low birth weight have been reported in the majority of studies considering mild to moderate maternal anemia (in contrast to our study where the mothers had severe anemia). Many studies indicated that routine iron supplementation during pregnancy may have beneficial effects on pregnancy outcome. Severe anemia in pregnancy may have adverse effects for the newborn and should be treated or prevented early in pregnancy.