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Biological mechanisms that might underlie iron's effects on fetal growth and preterm birth
1Program in International Nutrition, Department of Nutrition, University of California, Davis, CA, USA.
Insights
Anemia and iron deficiency in pregnant women may lead to low birth weight and preterm delivery through biological mechanisms like hypoxia and increased stress hormones. Further research via iron supplementation trials is recommended.
Area of Science:
- Obstetrics and Gynecology
- Maternal-Fetal Medicine
- Nutritional Science
Background:
- Maternal anemia and iron deficiency are linked to adverse pregnancy outcomes like low birth weight and preterm delivery.
- The precise biological mechanisms underlying these associations require further elucidation.
- Maternal nutritional status significantly influences pregnancy outcomes, particularly preterm delivery.
Purpose of the Study:
- To explore potential biological pathways through which anemia and iron deficiency may cause low birth weight and preterm delivery.
- To identify how maternal nutritional status impacts the risk of preterm delivery.
- To propose areas for future research, including iron supplementation trials.
Main Methods:
- Review of existing literature on anemia, iron deficiency, and pregnancy outcomes.
- Identification and analysis of potential biological mechanisms linking anemia/iron deficiency to adverse fetal development and preterm labor.
- Exploration of the role of stress hormones (e.g., corticotropin-releasing hormone) and oxidative damage.
Main Results:
- Anemia-induced hypoxia and iron deficiency-induced increased norepinephrine can elevate corticotropin-releasing hormone (CRH) levels.
- Elevated CRH is associated with preterm labor, pregnancy-induced hypertension, and premature rupture of membranes.
- Iron deficiency may increase oxidative stress and susceptibility to infections, further impacting pregnancy.
Conclusions:
- Anemia and iron deficiency present plausible biological mechanisms for causing low birth weight and preterm delivery.
- CRH, oxidative stress, and maternal infections are key potential mediators.
- Randomized, controlled iron supplementation trials are crucial to confirm these mechanisms and guide interventions.
Abstract:
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.