Iron in Pregnancy: Why It Matters and How to Get Enough

Iron deficiency is the most common nutritional deficiency in pregnancy worldwide, and Australia is no exception. Up to one in three pregnant women develop iron deficiency anaemia at some point during their pregnancy — and a significant proportion of them don't know it, because the symptoms closely resemble the tiredness and breathlessness that pregnancy produces anyway.

This overlap is the problem. When fatigue is attributed to pregnancy rather than investigated, iron deficiency goes untreated. And untreated iron deficiency has real consequences — for your energy, your immune function, your mental health, your birth outcomes, and your baby's iron stores after birth.

The good news is that iron deficiency in pregnancy is well understood, routinely screened for, and very manageable with the right combination of diet and supplementation. Here's what you need to know.

Why iron needs increase so significantly during pregnancy

Before pregnancy, the recommended daily iron intake for women of reproductive age is 18 milligrams per day. During pregnancy, that increases to 27 milligrams per day — a 50 percent increase — for several reasons that compound across the trimesters.

Your blood volume increases by approximately 50 percent during pregnancy to support your growing baby, placenta, and the increased demands on your heart and kidneys. This expansion requires a significant increase in red blood cell production, which in turn requires iron. Without adequate iron, your body cannot produce enough red blood cells to maintain normal oxygen delivery — the defining feature of iron deficiency anaemia.

Your baby also draws iron from your stores throughout pregnancy, particularly in the third trimester when they build their own iron reserves for the first six months of life, during which breast milk provides limited iron. This fetal demand continues regardless of your own iron levels — your body prioritises iron delivery to your baby, which means your own stores are depleted first.

The third source of iron demand is the placenta itself, which requires iron to function. By the time you factor in your expanded blood volume, your baby's requirements, and the placenta, the total iron demand of a full-term pregnancy is around 1,000 milligrams above baseline — a significant increase that diet alone often cannot fully meet.

When iron deficiency typically develops

Iron deficiency in pregnancy tends to follow a predictable pattern across the trimesters, though individual variation is significant.

In the first trimester, many women arrive at pregnancy with already-low iron stores from menstrual losses and inadequate dietary intake. The iron demands of early pregnancy are relatively modest, but nausea and food aversions frequently reduce dietary iron intake at exactly the point when it matters. Women who were borderline low before pregnancy often become deficient early.

In the second trimester, blood volume expansion accelerates and the gap between iron intake and iron demand widens for many women. This is the trimester when routine antenatal blood tests first check iron levels, and when iron supplementation is most commonly first prescribed.

In the third trimester, fetal iron demand is at its highest and maternal iron stores are typically at their lowest. Anaemia in the third trimester is associated with increased fatigue, reduced birth weight, preterm birth, and a higher likelihood of requiring blood transfusion during or after birth. It also reduces your capacity to cope with the blood loss that accompanies birth, which for most women is between 300 and 500 millilitres.

Symptoms of iron deficiency in pregnancy

The challenge with identifying iron deficiency in pregnancy is that its symptoms closely overlap with normal pregnancy experiences. Fatigue, breathlessness with mild exertion, difficulty concentrating, and pallor are all common in pregnancy regardless of iron status. This is why blood testing rather than symptom assessment is the only reliable way to know whether your iron levels are adequate.

More specific symptoms that suggest iron deficiency rather than general pregnancy fatigue include fatigue that is significantly out of proportion to your activity level, breathlessness at rest or with very minimal exertion, heart palpitations, headaches that are persistent rather than occasional, pallor of the inner eyelids and gums, and a strong craving for non-food substances including ice, soil, or chalk — a symptom called pica that is strongly associated with iron deficiency.

If you have any of these symptoms and haven't recently had iron levels checked, raise it with your midwife or GP at your next appointment rather than waiting for a routine blood test.

How iron levels are tested in pregnancy

Iron status is assessed through a blood test that typically includes several markers. Haemoglobin measures the concentration of the oxygen-carrying protein in your red blood cells and is the most commonly used indicator of anaemia. Ferritin measures your stored iron and is a more sensitive early indicator of depletion than haemoglobin, which only falls once stores are significantly depleted.

In Australia, iron levels are routinely checked at the booking blood test in the first trimester and again at around 28 weeks. Additional testing is ordered if symptoms suggest deficiency or if results are borderline. Your GP or midwife will interpret your results in the context of your full blood picture and your specific pregnancy rather than in isolation.

Normal haemoglobin thresholds during pregnancy are slightly lower than outside pregnancy because of blood volume dilution — a haemoglobin level that would indicate anaemia in a non-pregnant person may be normal in pregnancy. This is why results need to be interpreted by your care team rather than self-assessed.

Dietary sources of iron

Iron in food comes in two forms with very different absorption rates. Haem iron, found in animal products, is absorbed at around 25 percent efficiency. Non-haem iron, found in plant foods and fortified products, is absorbed at around 5 to 10 percent efficiency. This difference is significant when planning dietary iron intake, particularly for women who eat limited or no meat.

Haem iron sources worth including regularly: lean red meat including beef and lamb, which are among the richest dietary sources of iron available. Chicken and turkey provide less haem iron than red meat but still contribute meaningfully. Fish and shellfish, particularly oysters, mussels, and sardines, are good sources. Organ meats including liver are very high in iron but should be consumed in limited amounts during pregnancy due to very high vitamin A content — once a week at most.

Non-haem iron sources worth including regularly: lentils, chickpeas, kidney beans, and other legumes are among the most iron-rich plant foods and are also high in fibre and protein. Tofu, particularly firm tofu, is a useful source for women who eat little or no meat. Dark leafy greens including spinach, silverbeet, and kale contribute iron alongside folate. Fortified breakfast cereals provide a significant amount of iron per serve and are one of the most accessible sources for women who find other iron-rich foods difficult during nausea.

How to improve iron absorption from food

The absorption of non-haem iron — the type in plant foods — is significantly affected by what you eat alongside it. Understanding these interactions allows you to get considerably more value from plant-based iron sources.

Vitamin C dramatically improves non-haem iron absorption. Eating vitamin C-rich foods alongside iron-rich plant foods increases absorption by up to four times. Practical combinations include spinach with lemon dressing, lentil soup with a squeeze of lime, fortified cereal with fresh berries, or tofu stir-fry with capsicum and tomato.

Tea and coffee inhibit non-haem iron absorption when consumed with or immediately after iron-rich meals. The tannins in both beverages bind to non-haem iron and reduce its absorption by 50 to 60 percent. Waiting at least one hour after an iron-rich meal before drinking tea or coffee makes a meaningful difference, particularly for women who rely on plant-based iron sources.

Calcium inhibits iron absorption when consumed simultaneously. Dairy products and calcium-fortified foods are best eaten separately from iron-rich meals rather than alongside them. This is a practical consideration for women taking both calcium and iron supplements — they should be taken at different times of day rather than together.

Haem iron from animal sources is not affected by these interactions to the same degree. Tea, coffee, and calcium reduce the absorption of haem iron far less than non-haem iron, which is one reason why dietary iron adequacy is considerably easier to achieve for women who eat red meat regularly.

Iron supplementation during pregnancy

For many women, dietary iron alone is insufficient to meet the increased demands of pregnancy, particularly in the second and third trimesters. Iron supplementation is recommended when blood tests confirm deficiency or when dietary intake is consistently inadequate.

There are several forms of supplemental iron with different absorption rates and side effect profiles. Ferrous sulphate is the most commonly prescribed form in Australia and is well-absorbed, though it frequently causes gastrointestinal side effects including constipation, nausea, and dark stools. Ferrous gluconate and ferrous fumarate are gentler on the digestive system for many women, with slightly lower but still effective absorption. Liquid iron preparations are available for women who cannot tolerate tablet forms.

Taking iron supplements on an empty stomach improves absorption but increases the likelihood of gastrointestinal side effects. Taking them with a small amount of vitamin C-rich food or juice and away from tea, coffee, and calcium-rich foods optimises absorption while reducing side effects. If constipation is a significant problem, increasing dietary fibre and fluid intake alongside the supplement helps, as does discussing alternative forms with your GP.

Standard pregnancy multivitamins typically contain between 8 and 18 milligrams of iron — adequate as a preventive measure but insufficient for treating established deficiency. Women with diagnosed iron deficiency anaemia typically require a separate, higher-dose iron supplement in addition to their multivitamin.

Do not self-prescribe high-dose iron supplementation. Excess iron has its own risks including oxidative stress and gastrointestinal damage. The correct dose is determined by your blood test results and your GP's assessment.

Iron and postpartum recovery

The third trimester iron demand doesn't end at birth. Postpartum blood loss, which ranges from 300 to 500 millilitres for most births and can be significantly higher in complicated deliveries, draws further on iron stores that may already be depleted. Iron deficiency in the postpartum period is associated with increased rates of postnatal depression, slower physical recovery, and reduced milk supply in breastfeeding women.

Iron levels are checked at your six-week postnatal appointment if there were concerns during pregnancy or significant blood loss at birth. If you had iron deficiency anaemia in the third trimester, continuing iron supplementation postpartum and having your levels rechecked is worth discussing with your GP at your postnatal appointment.