Final answer:
A pregnant woman should consume 220 µg of iodine per day, which is an increase from the 150 µg recommended for non-pregnant adults. This additional intake supports the thyroid function and fetal development during pregnancy.
Step-by-step explanation:
During pregnancy, a woman's need for nutrients and energy increases to support the growth and development of the fetus, as well as the changes to her own body. For iodine specifically, which is critical for thyroid function and fetal brain development, the recommended dietary intake is higher for pregnant women. The normal iodine content in the body is 10 to 20 mg, with 70 to 80% of this present in the thyroid gland. The Food and Nutrition Board of the Institute of Medicine recommends that a pregnant woman consumes 220 µg of iodine per day. This is more than the 150 µg recommended for adult non-pregnant women. The additional iodide intake supports the enlarged thyroid gland and increased production of thyroid hormones necessary during pregnancy, which in turn supports normal fetal brain development.
It is important to understand that while the fetus relies on maternal iodine supply, the idea of 'eating for two' does not mean doubling nutritional intake across the board. In fact, the total amount of extra calories a pregnant woman needs is only about 300 per day on average, mostly during the last trimester. An excessive increase in caloric intake can lead to too much weight gain, which may be detrimental to both mother and baby. Therefore, nutrient intake should be adequate and balanced to support both maternal and fetal health, without excessive increases that could lead to other health concerns.