Studies suggests that too much milk is not good for pregnant women even though milk is an essential nutrient to pregnant mothers .
The researchers say while milk is an important source of calcium for mums-to-be, thousands of babies are born with iron deficiencies as a result.
Mother of three Rachel Leitch went out of her way to up her milk intake while pregnant - and five week old Sophie is a bundle of health.
But the new study suggests drinking three or more glasses a day could affect a little one's brain development.
"It's quite scary to think you have been doing something that is healthy and good for you and then you are finding out potentially you may've disadvantaged your children," Ms Leith says.
Umbilical cord blood samples taken from 131 children within the "Growing Up in New Zealand" study suggest 7 percent of Kiwi kids are born low in iron, which affects brain function
Associate Professor Cameron Grant, consultant paediatrician at Starship Children's Hospital, says although milk is a good source of calcium, it is such not a good source of other nutrients.
"It's hard to absorb calcium from milk, and some people lose iron when they drink milk because it irritates the lining of their tummy."
Researchers are not saying to pregnant women "don't drink milk" - one or two glasses a day is fine. But they recommend getting iron through red meat and leafy greens with vitamin C supplements to help absorption.
Research shows Kiwi children under two are lagging behind the rest of the world.
They're twice as likely to be deficient in iron as those Australia, Europe and the United States.
Milk's not the only suspect though - obese children don't absorb iron either.
Professor Grant says New Zealand has taken a more "laissez-faire attitude"
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