Nutrient Needs During Pregnancy

Minerals

For the most part, requirements for minerals during pregnancy are not different from requirements for non-pregnant women of the same age. However, it is still important to evaluate whether or not an individual’s intake meets recommendations. Some common minerals to keep in mind with pregnant women are listed below.

calcium
magnesium
iron

Calcium
Most calcium is laid down during last trimester. Although this amount of calcium is significant (approximately 25-30 grams), it seems that maternal calcium needs do not increase. Instead, physiologic changes occur, making intestinal calcium absorption more efficient.

During pregnancy some women may not drink milk due to lactose intolerance, so reviewing calcium sources that are not milk-based is important. Other women may simply not have adequate calcium intakes and may need information about milk- and non-milk-based calcium sources. If a woman is still not able to consume enough calcium from food sources then a supplement may be needed.

Calcium supplementation has been suggested as a treatment for pregnancy-induced hypertension. This is discussed in Module 4.

Magnesium
The RDA for magnesium during pregnancy is set at an additional 35 mg per day.

Iron
Iron requirements are increased during pregnancy, to support the growing fetus and placenta and also to support increased maternal red blood cells. Iron absorption is increased during pregnancy and maternal stores are mobilized. Anemia during pregnancy can increase the risk of low birthweight and of iron deficiency in the infant.

Iron needs increase in the second, and again in the third trimester. The DRIs for iron for pregnant women are based on estimated needs during the third trimester of pregnancy, in order to build iron stores during the first trimester.

Iron intakes in the US are generally below recommendations, so in many cases, supplementation is necessary during pregnancy. There are some compliance issues around iron supplements during pregnancy. Some women have noted constipation and/or nausea when taking supplements. Dietitians should keep this in mind when talking to clients. Usually taking iron with a meal can help decrease the nausea and trying other ways such as walking and increasing fluids to help with the constipation. Other suggestions for women who have difficulty taking vitamins include splitting the supplement (e.g., half in the morning and half in the evening) or using a children's chewable vitamin with iron.

One safety issue to note is that iron supplements contribute to a leading cause of poisoning deaths in US children under 6 years or age; children ingest their mother’s iron tablets because they look like candy.