Pregnancy support- Pathology

Preterm Birth - 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 birth

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

Iron supplementation in pregnancy

J Perinat Med. 2003;31(5):420-6

Müngen E.

Iron deficiency is the most common nutritional disorder in the world. Pregnant women are at especially high risk for iron deficiency and iron deficiency anemia. A considerable proportion of pregnant women in both developing and industrialized countries become anemic during pregnancy. The prevalence of anemia in pregnant women has remained unacceptably high worldwide despite the fact that routine iron supplementation during pregnancy has been almost universally recommended to prevent maternal anemia, especially in developing countries over the past 30 years. The major problem with iron supplementation during pregnancy is compliance. Despite many studies, the relationship between maternal anemia and adverse pregnancy outcome is unclear. However, there is now sufficient evidence that iron supplements increase hemoglobin and serum ferritin levels during pregnancy and also improve the maternal iron status in the puerperium, even in women who enter pregnancy with adequate iron stores. Recent information also suggests an association between maternal iron status in pregnancy and the iron status of infants postpartum. The necessity of routine iron supplementation during pregnancy has been debated in industrialized countries and routine supplementation is not universally practiced in all these countries. In view of existing data, however, routine iron supplementation during pregnancy seems to be a safe strategy to prevent maternal anemia in developing countries, where traditional diets provide inadequate iron and where malaria and other infections causing increased losses are endemic.

Publication Types:

• Review

Iron supplementation during pregnancy: what are the risks and benefits of current practices?

Appl Physiol Nutr Metab. 2007 Apr;32(2):282-8

Rioux FM, LeBlanc CP.

Iron-deficiency anemia is still prevalent among pregnant women living in industrialized countries such as Canada. To prevent this deficiency, iron supplements (30 mg/d) are routinely prescribed to Canadian pregnant women. Recently, dietary reference intakes for iron have increased from 18 and 23 mg/d during the second and third trimesters, respectively, to 27 mg/d throughout the pregnancy for all age groups. Whether this new recommendation implies an increase of iron dosage in supplements has not been answered. Are there any benefits or risks for the mother and her infant associated with iron supplementation during pregnancy? If iron supplementation is recommended, what should be the ideal dosage? This article reviews current knowledge on the potential negative or positive impact of iron supplementation during pregnancy on the outcomes of both infants and mothers. Based on the literature reviewed, a low daily dose of iron (30 mg elemental iron) during pregnancy improves women's iron status and seems to protect their infants from iron-deficiency anemia. Several studies have also shown that a low daily dose of iron may improve birth weight even in non-anemic pregnant women. However, higher dosages are not recommended because of the potential negative effects on mineral absorption, oxidative pathways, and adverse gastrointestinal symptoms. To date, it is still not clear if health professionals should recommend routine or selective supplementation. However, neither routine nor selective iron supplementation during pregnancy is able to eliminate iron-deficiency anemia. Even though the dietary reference intake for iron during pregnancy has been recently increased, we do not recommend higher doses of iron in supplements designed for pregnant women.

Publication Types:

• Review

Publication Types:

• Review

Publication Types:

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Publication Types:

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Publication Types:

• Review