Pregnancy support- Vitamin Deficiencies

Iron - updated: 03 November 2008

Iron status during pregnancy: setting the stage for mother and infant

Am J Clin Nutr. 2005 May;81(5):1218S-1222S

Scholl TO.

Supplementation with iron is generally recommended during pregnancy to meet the iron needs of both mother and fetus. When detected early in pregnancy, iron deficiency anemia (IDA) is associated with a > 2-fold increase in the risk of preterm delivery. Maternal anemia when diagnosed before midpregnancy is also associated with an increased risk of preterm birth. Results of recent randomized clinical trials in the United States and in Nepal that involved early supplementation with iron showed some reduction in risk of low birth weight or preterm low birth weight, but not preterm delivery. During the 3rd trimester, maternal anemia usually is not associated with increased risk of adverse pregnancy outcomes and may be an indicator of an expanded maternal plasma volume. High levels of hemoglobin, hematocrit, and ferritin are associated with an increased risk of fetal growth restriction, preterm delivery, and preeclampsia. While iron supplementation increases maternal iron status and stores, factors that underlie adverse pregnancy outcome are considered to result in this association, not iron supplements. On the other hand, iron supplements and increased iron stores have recently been linked to maternal complications (eg, gestational diabetes) and increased oxidative stress during pregnancy. Consequently, while iron supplementation may improve pregnancy outcome when the mother is iron deficient it is also possible that prophylactic supplementation may increase risk when the mother does not have iron deficiency or IDA. Anemia and IDA are not synonymous, even among low-income minority women in their reproductive years.

Publication Types:

• Review

Biological mechanisms that might underlie iron's effects on fetal growth and preterm b

J Nutr. 2001 Feb;131(2S-2):581S-589S

Allen LH.

A negative association between anemia and duration of gestation and low birth weight has been reported in the majority of studies, although a causal link remains to be proven. This paper explores potential biological mechanisms that might explain how anemia, iron deficiency or both could cause low birth weight and preterm delivery. The risk factors for preterm delivery and intrauterine growth retardation are quite similar, although relatively little is understood about the influence of maternal nutritional status on risk of preterm delivery. Several potential biological mechanisms were identified through which anemia or iron deficiency could affect pregnancy outcome. Anemia (by causing hypoxia) and iron deficiency (by increasing serum norepinephrine concentrations) can induce maternal and fetal stress, which stimulates the synthesis of corticotropin-releasing hormone (CRH). Elevated CRH concentrations are a major risk factor for preterm labor, pregnancy-induced hypertension and eclampsia, and premature rupture of the membranes. CRH also increases fetal cortisol production, and cortisol may inhibit longitudinal growth of the fetus. An alternative mechanism could be that iron deficiency increases oxidative damage to erythrocytes and the fetoplacental unit. Iron deficiency may also increase the risk of maternal infections, which can stimulate the production of CRH and are a major risk factor for preterm delivery. It would be useful to explore these potential biological mechanisms in randomized, controlled iron supplementation trials in anemic and iron-deficient pregnant women.

Publication Types:

• Review

Anemia and iron deficiency: effects on pregnancy outcome

Am J Clin Nutr. 2000 May;71(5 Suppl):1280S-4S

Allen LH.

This article reviews current knowledge of the effects of maternal anemia and iron deficiency on pregnancy outcome. A considerable amount of information remains to be learned about the benefits of maternal iron supplementation on the health and iron status of the mother and her child during pregnancy and postpartum. Current knowledge indicates that iron deficiency anemia in pregnancy is a risk factor for preterm delivery and subsequent low birth weight, and possibly for inferior neonatal health. Data are inadequate to determine the extent to which maternal anemia might contribute to maternal mortality. Even for women who enter pregnancy with reasonable iron stores, iron supplements improve iron status during pregnancy and for a considerable length of time postpartum, thus providing some protection against iron deficiency in the subsequent pregnancy. Mounting evidence indicates that maternal iron deficiency in pregnancy reduces fetal iron stores, perhaps well into the first year of life. This deserves further exploration because of the tendency of infants to develop iron deficiency anemia and because of the documented adverse consequences of this condition on infant development. The weight of evidence supports the advisability of routine iron supplementation during pregnancy.

Publication Types:

• Review

Publication Types:

• Review

Iron intake and iron status among adults in the Netherlands

Eur J Clin Nutr. 1997 Nov;51 Suppl 3:S51-8

Brussaard JH, Brants HA, Bouman M, Löwik MR.

OBJECTIVE: To assess the adequacy of iron intake and status, the prevalence of marginal iron status, the physiological and lifestyle factors influencing iron status and the role of dietary factors affecting the bioavailability of iron among Dutch adults. DESIGN: Food consumption was measured with 3 d diet records. Iron status and prevalence of iron deficiency and iron accumulation were evaluated using different criteria. Physical, biochemical and lifestyle characteristics were determined and relationships with iron status were evaluated by bi- and multivariate regression analysis. SUBJECTS: A sample of 444 adults, aged 20-79 y stratified for sex and 10 y age classes, with an overrepresentation of people with a low habitual intake of vitamin B6. RESULTS: Average iron intake was higher than the recommended daily allowance for the Netherlands in all sex-age groups except women aged 20-49, in which group average iron intake was 23% below the recommendation. Early iron deficiency, as reflected in low ferritin levels, was not found among men aged 20-49, but was observed in 5% of women aged 50-79, 11% of men aged 50-79, and 16% of women aged 20-49. Iron deficiency anaemia as reflected in low haemoglobin levels was found in 0-5% of the age-sex groups. Among men and women, 16% and 13% of variance in haemoglobin level, respectively, could be explained by physiological and dietary factors. For ferritin, the proportions were 36% and 34%, respectively. Iron status was correlated negatively with the vegetable fraction of the diet, and positively with factors from the animal fraction (haem iron, animal protein, meat). Further, haemoglobin was positively correlated with body weight among men, and with both age and use of oral contraceptives among women. Both among men and women, blood donorship in the six months prior to the study was negatively associated with serum ferritin levels. CONCLUSIONS: Women aged 20-49 are the adult sex-age group with the greatest risk of developing (an early stage of) iron depletion. The most important dietary factors influencing the iron status are the type of iron (haem/non-haem) and factors affecting the bioavailability of iron.

Publication Types:

• A sample of 444 adults

Iron deficiency in Europe

Public Health Nutr. 2001 Apr;4(2B):537-45

Hercberg S, Preziosi P, Galan P.

In Europe, iron deficiency is considered to be one of the main nutritional deficiency disorders affecting large fractions of the population, particularly such physiological groups as children, menstruating women and pregnant women. Some factors such as type of contraception in women, blood donation or minor pathological blood loss (haemorrhoids, gynaecological bleeding...) considerably increase the difficulty of covering iron needs. Moreover, women, especially adolescents consuming low-energy diets, vegetarians and vegans are at high risk of iron deficiency. Although there is no evidence that an absence of iron stores has any adverse consequences, it does indicate that iron nutrition is borderline, since any further reduction in body iron is associated with a decrease in the level of functional compounds such as haemoglobin. The prevalence of iron-deficient anaemia has slightly decreased in infants and menstruating women. Some positive factors may have contributed to reducing the prevalence of iron-deficiency anaemia in some groups of population: the use of iron-fortified formulas and iron-fortified cereals; the use of oral contraceptives and increased enrichment of iron in several countries; and the use of iron supplements during pregnancy in some European countries. It is possible to prevent and control iron deficiency by counseling individuals and families about sound iron nutrition during infancy and beyond, and about iron supplementation during pregnancy, by screening persons on the basis of their risk for iron deficiency, and by treating and following up persons with presumptive iron deficiency. This may help to reduce manifestations of iron deficiency and thus improve public health. Evidence linking iron status with risk of cardiovascular disease or cancer is unconvincing and does not justify changes in food fortification or medical practice, particularly because the benefits of assuring adequate iron intake during growth and development are well established. But stronger evidence is needed before rejecting the hypothesis that greater iron stores increase the incidence of CVD or cancer. At present, currently available data do not support radical changes in dietary recommendations. They include all means for increasing the content of dietary factors enhancing iron absorption or reducing the content of factors inhibiting iron absorption. Increased knowledge and increased information about factors may be important tools in the prevention of iron deficiency in Europe.

Publication Types:

• Review

Recommendations to prevent and control iron deficiency in the United States. Centers for Disease Control and Prevention

MMWR Recomm Rep. 1998 Apr 3;47(RR-3):1-29

Iron deficiency is the most common known form of nutritional deficiency. Its prevalence is highest among young children and women of childbearing age (particularly pregnant women). In children, iron deficiency causes developmental delays and behavioral disturbances, and in pregnant women, it increases the risk for a preterm delivery and delivering a low-birthweight baby. In the past three decades, increased iron intake among infants has resulted in a decline in childhood iron-deficiency anemia in the United States. As a consequence, the use of screening tests for anemia has become a less efficient means of detecting iron deficiency in some populations. For women of childbearing age, iron deficiency has remained prevalent. To address the changing epidemiology of iron deficiency in the United States, CDC staff in consultation with experts developed new recommendations for use by primary health-care providers to prevent, detect, and treat iron deficiency. These recommendations update the 1989 "CDC Criteria for Anemia in Children and Childbearing-Aged Women" (MMWR 1989;38(22):400-4) and are the first comprehensive CDC recommendations to prevent and control iron deficiency. CDC emphasizes sound iron nutrition for infants and young children, screening for anemia among women of childbearing age, and the importance of low-dose iron supplementation for pregnant women.

Publication Types:

• CDC publication

Iron deficiency--United States, 1999-2000

MMWR Morb Mortal Wkly Rep. 2002 Oct 11;51(40):897-9

Centers for Disease Control and Prevention (CDC).

Iron deficiency, the most common nutritional deficiency worldwide, has negative effects on work capacity and on motor and mental development in infants, children, and adolescents, and maternal iron deficiency anemia might cause low birthweight and preterm delivery. Although iron deficiency is more common in developing countries, a significant prevalence was observed in the United States during the early 1990s among certain populations, such as toddlers and females of childbearing age. One of the national health objectives for 2010 is to reduce iron deficiency in these vulnerable populations by 3-4 percentage points (objective no. 19-12). CDC has published recommendations to prevent iron deficiency in the United States. To characterize the iron status of persons in the United States, CDC calculated the prevalence of iron deficiency and iron deficiency anemia by applying a multiple-indicator model to data from the 1999-2000 National Health and Nutrition Examination Survey (NHANES 1999-2000). These values were compared with those observed in the third National Health and Nutrition Examination Survey (NHANES III [1988-1994]) using the same multiple-indicator model. This report summarizes the results of this analysis, which indicate that iron deficiency remains 2-5 percentage points above the 2010 national health objectives. To prevent iron deficiency, vulnerable populations should be encouraged to eat iron-rich foods and breast-feed or use iron-fortified formula for infants.

Publication Types:

• CDC publication

Publication Types:

• Review

Publication Types:

• Review

Publication Types:

• Review