More Than a Fatigue Problem
Low Ferritin Before Pregnancy
When we talk about preparing the body for pregnancy, we tend to focus on folate, prenatal vitamins, hormones, ovulation, and egg quality.
One nutrient that deserves much more attention is iron.
Iron deficiency is often reduced to a conversation about fatigue. You feel tired, your clinician checks your hemoglobin, and if you are not technically anemic, you may be told everything looks fine.
But iron does far more than help you feel energetic.
Iron is necessary for oxygen transport, cellular energy production, DNA synthesis, red blood cell production, placental development, and fetal growth. During pregnancy, the demand for iron rises substantially because the mother's body is expanding its own blood volume while simultaneously supporting the placenta and developing baby.
That is why we believe iron status deserves attention before conception whenever possible, not only after anemia appears during pregnancy.
Ferritin Is Your Iron Savings Account
One of the easiest ways to understand ferritin is to think about the difference between your checking account and your savings account.
Serum iron tells us something about the iron circulating in your blood at that particular moment.
Ferritin is a protein that stores iron and gives us an estimate of the iron reserves available for future needs.
Hemoglobin is the iron-containing protein inside red blood cells that carries oxygen.
This distinction matters because hemoglobin can remain normal while iron stores are already becoming depleted. Iron deficiency can therefore develop before conventional anemia appears. In pregnancy, ACOG uses a ferritin below 30 ng/mL as a diagnostic threshold for iron deficiency, while the WHO has historically used a lower threshold of 15 ng/mL in the first trimester.
A ferritin of 10, 15, or 20 should not simply be dismissed because someone's hemoglobin is still within the laboratory reference range.
The body may still be compensating.
Pregnancy dramatically increases the demand placed on that system.
What Does Iron Actually Do?
Iron is best known for its role in hemoglobin, but its biological responsibilities extend far beyond red blood cells.
Iron supports:
Hemoglobin production and oxygen delivery
Myoglobin and oxygen utilization in muscle
Mitochondrial energy production
DNA synthesis and cell division
Enzyme function
Neurological development
Placental growth and function
Maternal blood volume expansion
Fetal growth and development
Pregnancy increases the recommended dietary allowance for iron from 18 mg per day in nonpregnant adult women to 27 mg per day during pregnancy. The body needs additional iron to make the extra blood required to support both mother and baby.
This is why entering pregnancy with depleted iron stores can be very different from entering pregnancy with adequate reserves.
You are not just preparing for nine months of pregnancy.
You are preparing for the enormous physiological investment required to build another human being.
How Iron Moves Through the Body
Iron metabolism is a little more complicated than "eat iron and make blood."
Think of it as a supply chain.
Step 1: Iron enters the bloodstream
Iron is absorbed primarily through the gastrointestinal tract. Once absorbed, it enters circulation and binds primarily to a transport protein called transferrin.
This is one reason serum iron alone does not give us the entire picture. Serum iron can fluctuate based on factors including food intake and time of day. Looking at serum iron together with transferrin or total iron-binding capacity allows us to calculate transferrin saturation, which helps show how much iron is actually available for delivery.
Step 2: Iron is transported where it is needed
Transferrin essentially acts like the delivery vehicle.
It carries iron through the bloodstream to tissues that need it, including the bone marrow.
Step 3: Some iron is placed into storage
Iron that is not immediately needed can be stored inside ferritin.
Ferritin is found throughout the body, particularly in the liver, spleen, and bone marrow.
Think of ferritin as the reserve supply the body can draw from when iron demand increases.
Step 4: The bone marrow uses iron to manufacture red blood cells
Developing red blood cells in the bone marrow require iron to make hemoglobin.
Hemoglobin then allows mature red blood cells to carry oxygen from the lungs to tissues throughout the body.
So, very simply, the pathway looks something like this:
Dietary or supplemental iron → absorption → serum iron carried by transferrin → storage as ferritin or delivery to tissues → bone marrow → hemoglobin → oxygen-carrying red blood cells
The body continuously recycles iron from aging red blood cells, but pregnancy creates additional demand that recycling alone cannot always meet.
Why Ferritin Before Pregnancy Matters
Imagine becoming pregnant with a nearly empty savings account.
For a while, everything may look okay.
Then the expenses start arriving.
Pregnancy requires substantial iron for maternal red blood cell expansion, the placenta, and the developing fetus. By the third trimester, iron deficiency becomes increasingly common. NIH's Office of Dietary Supplements estimates that approximately 10 to 16 percent of women in the United States experience iron deficiency during pregnancy, increasing to roughly 25 percent during the third trimester. And it is especially common in women who have back to back pregnancies.
If iron stores are already depleted before conception, there is less reserve available to meet those increasing demands.
This is one reason we want to identify and address iron deficiency before pregnancy whenever possible.
Iron and Fertility
Iron's relationship with fertility is still an evolving area of research, and we should be careful not to imply that low ferritin is a single cause of infertility.
Fertility is multifactorial.
However, iron participates in fundamental processes required for reproduction, including cellular energy production, DNA synthesis, oxygen delivery, and rapidly dividing tissue development.
Women who menstruate heavily are particularly vulnerable to entering their reproductive years with depleted iron stores. Someone can also have iron deficiency without anemia, meaning hemoglobin remains normal even while available iron reserves are declining.
When we are helping someone prepare for pregnancy, we want to ask a broader question than:
"Are you anemic?"
We want to know:
"Does your body have the nutritional and hematologic resources to support conception, pregnancy, placental development, fetal growth, delivery, and postpartum recovery?"
Those are very different questions.
Your Baby Needs Iron Too
Once pregnancy begins, iron is no longer supporting one body.
It is supporting two.
The developing baby depends on maternal iron availability to support growth, blood formation, oxygen delivery, and neurological development.
Maternal iron deficiency during pregnancy has been associated with increased risks of anemia, preterm birth, low birth weight, and impaired cognitive and behavioral development in children.
Micronutrient requirements also increase during pregnancy specifically because nutrients including iron are essential for normal physiological function, growth, and development.
This is an important distinction.
Iron is not simply a nutrient that keeps Mom from feeling tired.
It is part of the raw material required to build the placenta, expand maternal blood volume, deliver oxygen, and support a developing baby's rapidly growing tissues.
Then Comes Delivery
Pregnancy is only part of the equation.
Eventually, the body has to deliver the baby.
Labor is an extraordinarily energy-intensive physiological event. Muscles need oxygen. The heart is working harder. The uterus is contracting repeatedly. Maternal blood volume has expanded significantly.
And blood loss is expected during delivery.
If a woman enters labor already iron deficient or anemic, she has less hematologic reserve available to tolerate blood loss and recover afterward.
After delivery, the body then needs to continue producing red blood cells and recovering from pregnancy and blood loss while simultaneously healing, caring for a newborn, and potentially breastfeeding.
This is another reason we do not want to wait until late pregnancy to start thinking about iron.
Ideally, we build the reserve before the demand peaks.
Why We Look at More Than Ferritin
Ferritin is incredibly useful, but ferritin alone does not tell the entire story.
Ferritin can also behave as an acute-phase reactant, meaning inflammation can increase ferritin levels and potentially make iron stores appear better than they actually are.
Serum iron can fluctuate considerably.
Hemoglobin may remain normal during earlier stages of iron depletion.
MCV and MCH may not decline until deficiency has progressed.
Transferrin saturation can provide additional information about how much circulating transferrin is actually carrying iron.
This is why we prefer to look at the entire pattern.
We are not trying to chase one number.
We are trying to understand what is happening with iron absorption, transportation, storage, utilization, red blood cell production, and ongoing iron loss.
Labs to Ask Your Clinician For
If you are preparing for pregnancy, have heavy menstrual cycles, have previously been told you are anemic, or have symptoms suggestive of iron deficiency, consider discussing a more comprehensive evaluation with your clinician.
At minimum, we often want to see:
CBC with differential
Hemoglobin
Hematocrit
RBC count
MCV
MCH
MCHC
RDW
Complete iron studies
Ferritin
Serum iron
Total iron-binding capacity, or TIBC
Transferrin
Transferrin saturation
Depending on the patient's history and results, additional testing may include:
Reticulocyte count
Reticulocyte hemoglobin, when available
Vitamin B12
Folate
CRP and/or hs-CRP to provide context for inflammation
CMP
Thyroid testing when clinically appropriate
Vitamin D
Additional evaluation for heavy menstrual bleeding, gastrointestinal blood loss, malabsorption, or other causes of recurrent deficiency
A transferrin saturation below approximately 20 percent can support the diagnosis of iron deficiency, while reticulocyte hemoglobin can provide an earlier look at whether newly produced red blood cells have adequate access to iron.
The goal is not simply to identify that iron is low.
We want to understand why it became low and whether the body is actually recovering.
What About a Ferritin Under 15?
At our clinic, we recommend that women with ferritin below 50 ng/mL discuss IV iron therapy with one of our clinicians, particularly when deficiency is significant (under 25), symptoms are present, oral iron has not been effective or tolerated, there is ongoing blood loss, or pregnancy is being planned.
This is our clinical approach, not a universal guideline. ACOG's diagnostic threshold for iron deficiency during pregnancy is actually lower, at ferritin below 30 ng/mL, but treatment decisions depend on hemoglobin, gestational age, symptoms, oral iron tolerance and response, severity of deficiency, and the individual patient's medical history.
IV iron should be prescribed and administered under appropriate medical supervision because iron deficiency should be confirmed and the appropriate formulation and dose determined for the individual patient.
Pregnancy Is Not the Time to Ignore Poor Iron Absorption
For women who are already pregnant, supporting iron intake and absorption becomes especially important.
That may include adequate dietary iron, an appropriate prenatal vitamin, supplemental iron when indicated, pairing nonheme iron sources with vitamin C, and evaluating factors that may interfere with absorption.
ACOG specifically recommends iron-rich foods such as beef, turkey, beans, lentils, and iron-fortified foods, along with vitamin C-containing foods that help support absorption.
But simply taking more iron is not always the answer.
If ferritin and hemoglobin are not responding appropriately, we want to ask why.
Is there continued heavy bleeding?
Is iron being absorbed?
Is inflammation altering iron metabolism?
Is there gastrointestinal disease or another source of blood loss?
Are there additional nutritional deficiencies interfering with healthy red blood cell production?
Is the patient actually taking in enough absorbable iron to replace what she is losing?
This is where individualized evaluation becomes important.
Don't Wait Until the Third Trimester to Think About Iron
One of the most important conversations we can have with women preparing for pregnancy is that pregnancy preparation is about building reserves before the body needs them. We want folate available before neural tube development. We want adequate nutrition before conception. And we want iron available before maternal blood volume, placental development, and fetal growth dramatically increase the body's demand for it.
A normal hemoglobin does not always mean iron status is optimal. A single serum iron value does not tell us whether iron stores are adequate. And ferritin should not be interpreted without understanding the rest of the patient's blood work, inflammatory status, symptoms, menstrual history, diet, absorption, and pregnancy plans.
If you are preparing for pregnancy, this is an excellent time to ask for a CBC and complete iron panel rather than serum iron alone.
You can request these labs through your primary care provider or OB/GYN, schedule an appointment with one of our clinicians for a comprehensive evaluation, or order your labs directly through our lab shop and bring your results in for review.
Because when we prepare for pregnancy, our goal is not simply to get a lab value into the "normal" range.
Our goal is to give Mom the resources she needs to conceive, build a placenta, support fetal development, carry a pregnancy, deliver a baby, replace lost blood, and recover well afterward.
Iron deserves to be part of that conversation.
References
American College of Obstetricians and Gynecologists. Anemia in Pregnancy. Practice Bulletin No. 233. Obstetrics & Gynecology. 2021. Reaffirmed 2024.
Lewkowitz AK, Tuuli MG. Identifying and treating iron deficiency anemia in pregnancy. American Society of Hematology Education Program. 2023.
National Institutes of Health, Office of Dietary Supplements. Dietary Supplements and Life Stages: Pregnancy. Health Professional Fact Sheet.
American College of Obstetricians and Gynecologists. Healthy Eating During Pregnancy.
World Health Organization. Multiple micronutrient supplementation during pregnancy. Updated August 2023.
Ning S, Zeller MP. Management of iron deficiency. American Society of Hematology Education Program. 2019.
Breymann C, Auerbach M. Iron deficiency in gynecology and obstetrics: clinical implications and management. American Society of Hematology Education Program. 2017.
This article is for educational purposes only and is not intended to diagnose, treat, or replace individualized medical care. Iron supplementation and IV iron therapy should be guided by appropriate laboratory testing and a qualified healthcare professional.