Nutrition Science and Everyday Application - beta v 0.1

580 ALICE CALLAHAN, PHD, HEATHER LEONARD, MED, RDN, AND TAMBERLY POWELL, MS, RDN
and iodized salt. However, iodine intake in the U.S. has declined in recent decades as more
people watch their intake of table salt and/or switch to kosher or sea salt, which aren’t
iodized. In addition, processed foods are generally made with non-iodized salt, and the
intake of processed foods has increased. Meanwhile, the popularity of dairy products has
declined. Most people in the U.S. still consume enough iodine to meet their requirement,
but pregnant women may be at risk for iodine deficiency because of their increased need
for this mineral. Iodine deficiency during pregnancy can cause miscarriage, stillbirth, and
major neurodevelopmental deficits and growth retardation in the fetus. 16 Unfortunately,
many prenatal vitamins do not contain iodine, so it’s worth checking the label to ensure that
iodine is included. 17
The micronutrients involved with building the skeleton—vitamin D, calcium, phosphorus,
and magnesium—are crucial during pregnancy to support fetal bone development. Although
the levels are the same as those for nonpregnant women, many women do not typically
consume adequate amounts and should make an extra effort to meet those needs.
As always, it’s important to read supplement labels carefully, with the aim of choosing a
prenatal supplement that contains close to the RDA or AI for micronutrients and avoiding
those that exceed the UL, unless under the specific direction of a healthcare provider. In
particular, both vitamin A and zinc consumed in excessive amounts can cause birth defects.
Beta-carotene is typically used as the vitamin A source in prenatal supplements, because
unlike vitamin A, it doesn’t cause birth defects (see Unit 8).
FOODS AND OTHER SUBSTANCES TO AVOID
It’s not just nutrients that can cross the placenta. Other substances such as alcohol, nicotine,
cannabinoids (from cannabis), and both prescription and recreational drugs can also pass
from mother to fetus. Exposure to these substances can have lasting and detrimental effects
on the health of the fetus. For this reason, pregnant women are advised to avoid using
alcohol, tobacco, cannabis, and recreational drugs during pregnancy. Medical providers can
help pregnant women quit using these substances and advise them on the safety of specific
medications needed during pregnancy. 1
Some substances are so detrimental that a woman should avoid them even if she suspects
that she might be pregnant. For example, consumption of alcoholic beverages results in
a range of abnormalities that fall under the umbrella of fetal alcohol spectrum disorders.
They include learning and attention deficits, heart defects, and abnormal facial features
(Figure 11.5). Alcohol enters the fetus’s bloodstream via the umbilical cord and can slow
fetal growth, damage the brain, or even result in miscarriage. The effects of alcohol are most
severe in the first trimester, when the organs are developing. There is no known safe amount
of alcohol in pregnancy.