New mothers who don't get enough iron are more likely to have a difficult time bonding with their babies than women who take their vitamins, according to a study released.

Earlier studies have shown that anemic women may experience postpartum depression and moderate iron deficiency can slow thinking and memory. The Penn State study is the first to look at how iron deficiency affects new mothers' ability to tune in to their children emotionally.

"Our new results suggest that the effects of mild iron deficiency ... can disrupt the solid foundation that is established by healthy mother-infant interactions," said the study's lead author, Dr. Laura Murray-Kolb.

Women who forgo vitamin supplements commonly experience iron deficiency after childbirth, the researchers said.

Researchers videotaped 85 women in South Africa interacting with their infants 10 weeks after childbirth. In that group, 64 were identified as mildly iron-deficient; 31 had no deficiency. Half of the iron-deficient women were then given supplements and after nine months, all were again videotaped with their children.

Researchers who analyzed the video concluded that the mildly iron-deficient mothers who got no supplements were less sensitive to their babies' cues and scored lowered on measures of emotional availability than did the women in the other two groups.

At nine months, the babies of the three groups of mothers also behaved differently, with the toddlers of the mildly iron-deficient moms less responsive and less involved with their mothers, the study said.

"New mothers should be aware of their iron status, which we now know affects the child as well as the mother," Murray-Kolb said in a statement. "Iron deficiency is easy to correct and could be a big part of postpartum problems with mother-child interactions."