The findings, based on a study of South African mothers, are the first to reveal a link between iron deficiency and mother-child interactions. They could be important as young women are often deficient in the mineral.
Almost 24 per cent of pregnant mothers in Europe are thought to have iron deficiency anaemia while in the Americas this figure rises to 53 per cent, according to data from the WHO.
Dr Laura Murray-Kolb, a post-doctoral fellow in child development at Penn State University, and colleagues identified 64 women who were mildly iron deficient after childbirth and 31 who were not iron deficient.
At 10 weeks after childbirth, the women and their babies were videotaped interacting. Half of the iron-deficient women were then given iron supplements.
After nine months, all of the women, those who received supplements and those who did not, as well as the group of iron sufficient women, were videotaped interacting with their babies again.
Analysis of the tapes showed that the mothering of the women who were iron sufficient and those who received supplements differed from those who were mildly iron deficient on measures of emotional availability.
For example, observed in play interactions, the mildly iron-deficient mothers were less sensitive to their baby's cues, said the researchers, presenting their findings on Tuesday at the Experimental Biology meeting in San Diego, California.
They also scored lower on giving their babies chances to lead interactions. In addition, the iron-deficient mothers cut in on the baby's play at inappropriate times more often and appeared bored or distant more frequently than the other mothers.
At nine months, the babies of the three groups of mothers also behaved differently. For example, the babies of the mildly iron-deficient women were less responsive and less involved with their mothers. When moving away from a mildly iron-deficient mother, the baby would depend less on its mother for reassurance.
Dr Murray-Kolb said: "Our new results suggest that the effects of mild iron deficiency - which are easily correctable with supplements - can disrupt the solid foundation that is established by healthy mother/infant interactions."
The same team reported in January that iron supplementation resulted in a 25 per cent improvement in previously iron-deficient mothers' depression and stress scales.