[Severe maternal anemia and pregnancy outcome]

A systematic review and meta-analysis of the correlation between maternal and neonatal iron status and haematologic indices

BACKGROUND

Iron deficiency (ID) is the leading single-nutrient deficiency in the world. Anaemia is a common outcome of ID that affects half of pregnancies worldwide with serious consequences for child development. Whether haematologic indices and biomarkers of iron status in pregnant women correlate with those of their neonates is unclear. This systematic review evaluated studies comparing haematologic and iron status indices in pregnant women and their newborns/neonates.

METHODS

We searched MEDLINE, EMBASE, CINAHL, and Web of Science from database inception until March 2020 for primary studies comparing haematologic and iron status indices between women and their newborns up to 48 h after birth. We summarized the results descriptively and calculated pooled correlation coefficients in mothers and newborns/neonates using the Schmidt-Hunter method. The protocol was registered at PROSPERO International Prospective Register of Systematic Reviews (Registration number: CRD42018093094).

FINDINGS

Sixty-five studies were included. Pooled correlation coefficients for biomarkers of iron status in mothers and newborns/neonates were 0.13 (ferritin), 0.42 (hepcidin), 0.30 (serum/plasma iron), 0.09 (transferrin), 0.20 (transferrin saturation), and 0.16 (total iron binding capacity). Pooled correlation coefficients for haematological indices in mothers and newborns/neonates were 0.15 (haemoglobin), 0.15 (haematocrit), 0.25 (mean cell/corpuscular haemoglobin), 0.22 (mean cell/corpuscular volume).

INTERPRETATION

Maternal biomarkers of iron and haematologic status correlate poorly with those in newborns/neonates. These results underscore a need for alternative approaches to estimate foetal/neonatal iron status and haematological indices.

FUNDING

MBO and SLB hold Canada Research Chairs, and grants from the Women and Children's Health Research Institute and Canadian Institutes of Health Research.

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 Nutritional Status, Food Intake and Pregnancy Weight Gain in Nepal

Poor maternal nutrition during pregnancy may predispose to intrauterine growth restriction (IUGR), immunological and metabolic adaptations which manifest as low birth weight (LBW) and increase the risk of adult non-communicable disease. This study examined the relationships between maternal nutritional status, food intake and pregnancy weight gain (PWG) which may account for risk of LBW in Nepal.

A prospective cross-sectional study was undertaken in rural and urban Nepalese population using simple random sampling to select eligible subjects. Retrospective data was extracted from records and dietary intake was assessed using a Food Frequency Questionnaire and 24 Hour Dietary Recall.

A total of 376 women were recruited. A high prevalence of LBW (27.9 per cent) and preterm (14 per cent) delivery were observed. LBW was higher in rural than urban subjects ( p < 0.05). Birth weight was related to period of gestation ( r = 0.609, p < 0.05) ( r = 0.49, p < 0.001), energy intake ( r = 0.061, p < 0.001) and maternal protein intake ( r = 0.501, p < 0.001). Low PWG (8.11 kg) was also observed and was associated with protein ( r = 0.499, p < 0.01) and energy intake ( r = 0.396, p < 0.01) and were lower among mothers in rural areas ( p < 0.05). Calcium intake was related to crown heel length (CHL) ( r = 0.399, p < 0.001). Lipid, zinc and folate intake were significantly different in rural and urban subjects although the latter were adequate in both.

Findings demonstrate the impact of maternal nutrition on birth outcomes in relation to specific nutrients and components of the diet. Targeted interventions are supported by the findings of this study in both rural and urban areas of Nepal.

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.

Can anemia in the first trimester predict obstetrical complications later in pregnancy?

OBJECTIVE

The present study examines whether there is an association between anemia during the first trimester and the risk to develop preterm delivery (PTD), intrauterine growth restriction, and other obstetrical complications.

METHODS

The study population included all registered births between 2000 and 2010. Anemia was defined as hemoglobin <10 g/dl. A comparison of obstetrical characteristics and perinatal outcomes was performed between women with and without anemia. Multiple logistic regression models were used to control for confounders.

RESULTS

The study population included 33,888 deliveries, of these 5.1% (1718) were with anemia during the first trimester. Women with anemia were significantly older, delivered earlier, and were more likely to be grand multiparous. There were significantly higher rates of PTD and low birth weight (LBW; <2500 g) among patients with anemia (12.3% vs. 9.3%; p < 0.001 and 11.7% vs. 9.0%; p < 0.001, respectively). On the contrary, no significant differences between the groups were noted regarding the rate of intrauterine growth restriction. Using a multivariable analysis, the significant association between anemia and PTD persisted (OR = 1.35; 95% CI 1.2-1.6, p < 0.01).

CONCLUSIONS

Anemia during the first trimester is significantly and independently associated with an increased risk for subsequent PTD.

Relationship between maternal hemoglobin concentration and neonatal birth weight

OBJECTIVE

Pregnancy considerably increases iron needs in a mother and her fetus. The purpose of this study was to assess the relationship between maternal hemoglobin concentration in labor with neonatal birth weight.

METHODS

A population-based study in Shahid Sadughi Hospital in Yazd, Iran, was performed by comparing 1842 singleton term pregnancies of patients with and without anemia and their newborns. Maternal characteristics, including hemoglobin values, were recorded at the labor visit. Maternal anemia was defined as hemoglobin concentration lower than 10 g/dl during pregnancy. Main outcome measures included birth weight and Apgar score. Linear and logistic regression models were used to analyze data.

RESULTS

Anemia (Hb < 10 g/dl) was associated with a significantly increased risk of low birth weight (< 2500 g). High hemoglobin (> 13 g/dl) increased the risk of low birth weight but it was not significant. The risk of a low Apgar score was significantly increased in women with anemia. The minimum incidence of low birth weight occurs in association with a hemoglobin concentration of 10-13 g/dl.

CONCLUSIONS

Maternal anemia was significantly associated with effect on birth weight. Also Hb > 13 g/dl was also associated with an increased risk of low birth weight.

Identifying a window of vulnerability during fetal development in a maternal iron restriction model

It is well acknowledged from observations in humans that iron deficiency during pregnancy can be associated with a number of developmental problems in the newborn and developing child. Due to the obvious limitations of human studies, the stage during gestation at which maternal iron deficiency causes an apparent impairment in the offspring remains elusive. In order to begin to understand the time window(s) during pregnancy that is/are especially susceptible to suboptimal iron levels, which may result in negative effects on the development of the fetus, we developed a rat model in which we were able to manipulate and monitor the dietary iron intake during specific stages of pregnancy and analyzed the developing fetuses. We established four different dietary-feeding protocols that were designed to render the fetuses iron deficient at different gestational stages. Based on a functional analysis that employed Auditory Brainstem Response measurements, we found that maternal iron restriction initiated prior to conception and during the first trimester were associated with profound changes in the developing fetus compared to iron restriction initiated later in pregnancy. We also showed that the presence of iron deficiency anemia, low body weight, and changes in core body temperature were not defining factors in the establishment of neural impairment in the rodent offspring.Our data may have significant relevance for understanding the impact of suboptimal iron levels during pregnancy not only on the mother but also on the developing fetus and hence might lead to a more informed timing of iron supplementation during pregnancy.

Plasma and urinary aluminum concentrations in severely anemic geophagous pregnant women in the Bas Maroni region of French Guiana: a case-control study

The clays consumed by geophagous individuals contain large quantities of aluminum, a known neurological and hematological toxin. This is the first study to evaluate the risk of aluminum poisoning in geophagous individuals. Blind determinations of plasma and urinary aluminum concentrations were carried out in 98 anemic geophagous pregnant women and 85 non-anemic non-geophagous pregnant women. Aluminum concentrations were significantly higher (P < 0.0001) in the geophagous anemic women than in the controls, with odds ratios of 6.83 (95% confidence interval [CI] = 2.72-19.31) for plasma concentrations (13.92 ± 14.09 μg/L versus 4.95 ± 7.11 μg/L) and 5.44 (95% CI = 2.17-14.8) for urinary concentrations (92.83 ± 251.21 μg/L versus 12.11 ± 23 μg/L). The ingested clay is the most likely source of this overexposure to aluminum. If confirmed, the clinical consequences of this absorption for pregnant women and their offspring should be explored.

ABO phenotype and other risk factors associated with chorioamnionitis

OBJECTIVE

To examine risk factors associated with chorioamnionitis.

STUDY DESIGN

We conducted a retrospective cohort study using data on women who delivered prematurely (< 37 weeks of gestation) over a 12-year period. Eleven potential risk factors were identified. Subjects were stratified according to their blood type into 2 groups: group 1, subjects with anti-B antibodies (blood types A and O), and group 2, subjects without anti-B antibodies (blood types B and AB). Univariate, bivariate, and logistic regression analyses were done to examine risk factors for chorioamnionitis while controlling for confounders.

RESULTS

The study included 2879 subjects, 96 of whom (3.3%) were diagnosed with chorioamnionitis. Chorioamnionitis increased significantly with alcohol use (adjusted odds ratio [AOR] = 4.7), prolonged rupture of membranes (ROM) (AOR = 4.16), anemia (AOR = 2.17), and group 1 status (AOR = 1.88). Advanced maternal age was protective of chorioamnionitis (AOR = 0.96).

CONCLUSION

Alcohol consumption during pregnancy, prolonged ROM, anemia, and blood types A and O are associated with increased risk for chorioamnionitis; advanced maternal age, with decreased risk. Further studies are needed to determine the efficacy of early prenatal care in the control of anemia and to examine its affect on the incidence of chorioamnionitis.