Will My Child Be Smarter If I Take Iron Supplements during Pregnancy? Effect of Iron Supplementation during Pregnancy on the Intelligence Quotient and Behavior of Children at 4 Years of Age: Long-Term Follow-Up of a Randomized Controlled Trial

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Taking iron as a nutritional supplement is a common practice during pregnancy. In fact, it is recommended by most health institutions around the world. However, experts are divided about whether iron should be regularly administered to pregnant women.

In some countries, pregnant women are routinely advised to take iron supplements, but in other countries, the policy is to provide iron and folic acid supplements only if the woman is diagnosed with anemia.

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Evidence from animal studies has consistently shown that insufficient iron during pregnancy can lead to permanent structural and functional changes in the offspring’s brain. Trials like this cannot be performed on humans for obvious ethical reasons.

A Human Study

A group of Australian scientists carried out a study entitled “Effect of Iron Supplementation during Pregnancy on the Intelligence Quotient and Behavior of Children at 4 Years of Age: Long-Term Follow-Up of a Randomized Controlled Trial.” They assessed whether improved iron nutrition during pregnancy (through routine iron supplementation) influences the development of the children and the long-term health of the mothers.

The mothers and children who had participated in a previous randomized trial about iron supplementation during pregnancy were eligible for this follow-up study. In the original trial, 430 pregnant women receiving prenatal care were recruited from 1997 to 1999. The participants were randomly assigned to receive either an iron supplement or a placebo from twenty weeks of gestation until birth. Women in the iron group had higher concentrations of hemoglobin and serum ferritin and lower incidences of iron deficiency and anemia at the end of pregnancy.

The follow-up was conducted four years after birth (from 2002 to 2004) because developmental assessment at preschool age is considered the best early predictor of school achievement.

Qualified psychologists administered Stanford-Binet Intelligence Scales to assess each child’s IQ (childhood intelligence quotient). Child behavior was assessed by using the Strength and Difficulties Questionnaire (SDQ), which is a behavior-screening questionnaire for parents used to evaluate behavioral problems and emotions.

The weight and height of the children were measured with an electronic scale and a stadiometer respectively. Data about sex, gestational age at birth, birth order, breastfeeding duration, parental education, and quality of home environment were collected.


Seventy percent of the mothers and children from the original trial were assessed four years after birth. At follow-up, there were no differences in the social and demographic characteristics of the families from both groups. The key difference between them was the higher iron levels of the iron-supplemented women versus the placebo group at the end of pregnancy.

Adjustments for other variables, such as maternal age, the parents’ education levels, the quality of the family environment, breastfeeding duration, the gestational age at birth, birth order, and the sex of the child did not change the results for either IQ or behavior.

The major finding is that routine iron supplementation during pregnancy did not benefit childhood IQ despite the clear increase in iron levels in the mothers at birth.

There was an unexpected higher frequency of abnormal behavior among the children in the iron group. This effect may have been due to chance since behavior was a secondary outcome, and there was only a small number of children with abnormal scores. Therefore, this result needs to be interpreted with caution.

From a public health perspective, the lack of apparent clinical benefit for either the mothers or the children and the potential hazards associated with routine iron supplementation during pregnancy suggest that the risks may outweigh the benefits, especially in well-nourished populations where the incidence of anemia at the end of pregnancy is low.

Further research is needed, particularly to study population subgroups in industrialized or underdeveloped countries that may benefit from iron supplementation during pregnancy.

Regardless of this study’s results, mothers should never stop taking nutritional supplements that have been prescribed by a doctor. In addition, international guidelines on pregnancy still recommend the intake of some supplements, especially iron and folic acid.


Zhou, Shao J., Robert A. Gibson, Caroline A. Crowther, Peter Baghurst, and Maria Makrides. “Effect of iron supplementation during pregnancy on the intelligence quotient and behavior of children at 4 y of age: long-term follow-up of a randomized controlled trial–.” The American journal of clinical nutrition 83, no. 5 (2006): 1112-1117. Retrieved from https://academic.oup.com

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