Ferritin is a protein that stores iron in the body, releasing it as needed. During pregnancy, the demand for iron escalates to support the mother’s increased blood volume and the growing fetus. The third trimester is a period of peak iron requirement, making adequate ferritin levels important for the health of both mother and baby.
Optimal Ferritin Levels During the Third Trimester
Defining an ideal ferritin level during the third trimester is complex, as values naturally decline. While laboratory reference ranges vary, many health organizations consider a serum ferritin level below 30 micrograms per liter (µg/L) to indicate iron deficiency. This is a more accurate threshold than the older 15 µg/L guideline. Without iron supplementation, it is common for ferritin levels to reach their lowest point between weeks 35 and 38.
It is helpful to distinguish between iron deficiency and iron-deficiency anemia. Iron deficiency, identified by low ferritin, means the body’s iron stores are depleted. Iron-deficiency anemia is a more advanced stage where low iron stores lead to a drop in hemoglobin. During pregnancy, a hemoglobin level below 105 grams per liter (g/L) in the third trimester is often classified as anemic.
The physiological changes of pregnancy drive this decline in ferritin. The mother’s blood volume expands by nearly 50% to support the placenta and fetus, diluting ferritin concentration in a process called hemodilution. At the same time, the baby’s accelerated growth requires a significant transfer of iron across the placenta. The daily iron requirement can increase to 7.5 milligrams per day, a demand that diet alone often cannot meet.
Impact of Low Ferritin on Mother and Baby
Depleted iron stores can affect the mother’s well-being and pregnancy outcomes. Common symptoms of low ferritin include:
- Fatigue that is more severe than typical pregnancy tiredness
- Weakness and shortness of breath upon exertion
- Difficulty concentrating or “brain fog”
- Restless legs syndrome, an urge to move the legs, especially at night
Beyond these symptoms, iron deficiency increases the risk of serious medical events. It contributes to postpartum hemorrhage, as iron is needed for proper uterine muscle function after delivery. Research also suggests a link between low iron status during pregnancy and a higher likelihood of developing postpartum depression.
The mother’s iron status directly links to the baby’s health. Maternal iron deficiency can lead to an increased risk of preterm delivery and low birth weight. Since iron is important for brain development and cognitive function, a baby born to an iron-deficient mother may have low iron stores, which can have lasting effects.
Strategies for Increasing Ferritin
Addressing low ferritin involves diet and, when necessary, supplementation. A primary strategy is to incorporate iron-rich foods. There are two forms of dietary iron: heme iron from animal products like red meat and poultry, and non-heme iron from plant sources like lentils, beans, and spinach. Heme iron is more readily absorbed by the body.
To improve the absorption of non-heme iron, consume it with foods rich in Vitamin C, such as pairing lentils with orange juice. Conversely, avoid consuming iron-rich meals with calcium-rich foods like milk, or with coffee and tea, as these can interfere with absorption.
When diet is insufficient, healthcare providers may recommend oral iron supplements, often dosed between 100-200 milligrams of elemental iron per day. Following the prescribed dosage is necessary to avoid side effects like constipation and nausea, as excessive intake does not increase absorption. Taking these supplements with Vitamin C can also aid absorption.
If a woman has severe iron-deficiency anemia, cannot tolerate oral iron, or is diagnosed late in pregnancy, a doctor may recommend intravenous (IV) iron. An IV infusion delivers iron directly into the bloodstream, bypassing the digestive system. This method raises iron levels much more quickly than oral supplements, which helps restore iron stores rapidly before delivery.