The researchers first completed a study among poor women in Nepal ten years ago.
During pregnancy some of the women received supplements containing iron and another micronutrient, folic acid.
Ms. Christian says that study showed the supplements could improve child survival.
Now the children are older.
The researchers returned to Nepal and tested their neurological development.
They found improved abilities among those whose mothers had received iron and folic acid during pregnancy and for three months after.
Another new study looks at levels of vitamin D in babies.
It says newborns with the lowest levels were twice as likely to develop respiratory infections as those with normal levels of vitamin D.
Vitamin D helps build strong bones and strengthens the body's defenses against disease.
The vitamin is commonly added to cow's milk and also found in supplements.
Vitamin D is called the sunshine vitamin.
The body naturally produces it from sunlight.
Carlos Camargo from Harvard Medical School in Massachusetts and other researchers did the study.
It followed more than nine hundred children in New Zealand until they were five years old.
Dr. Camargo said the problem of vitamin D deficiency is not limited to countries with the least sun.
There are low levels of vitamin D in people living in areas where there is a lot of sun.
This is because people are spending more time indoors.
For VOA Special English I'm Alex Villarreal.
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