Brain Rules for Baby by John Medina Read Free Book Online Page A

function of her brain volume. Brain size predicts about 20 percent of the variance in her IQ scores (her prefrontal cortex, just behind her forehead, is particularly prescient). Brain volume is related to birth weight, which means that, to a point, larger babies are smarter babies.
    The fuel of food helps grow a larger baby. Between four months and birth, the fetus becomes almost ridiculously sensitive to both the amount and the type of food you consume. We know this from malnutrition studies. Babies experiencing a critical lack of nutriment have fewer neurons, fewer and shorter connections between the neurons that exist, and less insulation all around in the second trimester. When they grow up, the kids carrying these brains exhibit more behavioral problems, show slower language growth, have lower IQs, get worse grades, and generally make poor athletes.
     
    IQ rises with birth weight, up to 8 pounds
    How big should baby grow? Here’s another balancing act. A baby’s IQ rises steadily with birth weight, up to about 8 pounds. The job is mostly done prior to this benchmark: There is only 1 IQ point difference between a 6.5-pounder and a 7.5-pounder. Above 9 pounds, IQ actually drifts down a bit, about 1 point on average. This loss probably occurs because larger babies are more likely to experience hypoxia—a restriction of oxygen—or other injuries during birth.
    How much do you need to eat? That depends upon how fit you are going into the pregnancy. The bad news is that 55 percent of women of childbearing age in the United States are already too fat. Their Body Mass Index, or BMI, which is a kind of a “gross domestic product” of how fat you are, is between 25 and 29.9. If that’s you, then you need to gain only about 15 to 25 pounds to create a healthy baby, according to the Institute of Medicine. You want to add about half a pound a week in the critical second and third trimesters of pregnancy. If you
are underweight, with a typical BMI of less than 18.5, you need to gain between 28 and 40 pounds to optimize your baby’s brain development. That’s about a pound a week in the critical last half of pregnancy. This is true for women of normal weight, too.
    So, the amount of fuel is important. There is increasing evidence that the type of fuel you eat during the critical period is important, too. The next balance comes between foods that a pregnant mom wants to eat and foods that are optimal for a baby’s brain development. Unfortunately, they are not always the same thing.
2. Eat just the right foods
    Women have strange experiences with food preferences during pregnancy, suddenly loving foods they used to loathe and loathing foods they used to crave. It’s not just pickles and ice cream, as any pregnant woman can tell you. One woman developed a craving for lemon juice on a burrito—a need that lasted for three months. Another wanted pickled okra. A surprising number crave crushed ice. Women can even desire things that aren’t food. An item that regularly makes the Top Ten List of Weird Pregnancy Cravings is baby talcum powder. So is coal. One woman wanted to lick dust. Pica is a common disorder: a craving lasting longer than a month for eating things that aren’t food, like dirt and clay.
    Is there any evidence you should pay attention to these cravings? Is the baby telegraphing its nutritional needs? The answer is no. There is some evidence that iron deficiencies can be consciously detected, but the data are thin. Mostly it’s a matter of how a person uses food in her daily life. An anxious person who is comforted by the chemicals in chocolate might grow to crave chocolate whenever she feels stressed. And a woman will feel stressed a lot during pregnancy. (This craving for chocolate reflects a learned response, not a biological need, though I think my wife would probably disagree.) We actually don’t know why a pregnant woman’s crazy cravings occur.

    That doesn’t mean the body doesn’t have nutritional