How to maintain your iron stores in pregnancy

Iron deficiency is one of the most common nutrient deficiencies world wide, affecting more than 25% of people. Approximately 12% of women enter pregnancy already iron deficient. This blog explores changes in iron status across trimesters, how women can work to maintain their iron stores and avoid interventions and whether it is actually reasonable to expect women to maintain iron levels.

The overall iron cost of pregnancy from conception through to delivery for the mother is 500mg – 1.2g. To put this into context women prior to pregnancy have a total iron content within their body of just 3g. It’s then no surprise that maintaining iron stores during pregnancy can be difficult, the maths doesn’t look promising, particularly for those 12% of women who enter pregnancy already deficient.

So how can you maintain your iron stores in pregnancy?

The first thing to note is that your ferritin (iron stores) levels, will drop during trimester 2 and 3 and this is normal and known as “physiological anaemia”. The best your iron status will ever look during pregnancy is in trimester 1. This is where preconception care plays a pivotal role in ensuring that you don’t end up needing an IV iron intervention in later stages of pregnancy.

In an ideal world working on your ferritin levels 3-6 months prior to conception, would allow you to work towards a ferritin level of between 50 ug/L – 100 ug/L. During this preconception period depending on your existing iron status ideally you are consuming between 3-5 serves of haem iron per week, this includes beef and lamb and possibly using a low dose iron supplement (I do not recommend using high dose iron such as Maltefor or Ferrograd-C, as these are ineffective and cause unwanted side effects such as constipation).

What changes to your iron status in trimester 2?

During trimester 2 (weeks 14 – 26) your ferritin levels will drop. This is a normal physiological response during pregnancy, and research shows that our current reference ranges for women do not account for this normal response.

As low iron and anaemia are so common in pregnancy iron studies are routinely checked at 28 weeks. The issue with this standard of care is that the normal state of physiological anaemia that occurs in pregnancy is often not taken into account, and it is common for women to be panic prescribed IV iron or high dose supplementation.

During trimester 2 something called haemodilution occurs, this simply means that plasma volume expands diluting the blood which causes both ferritin and haemoglobin (Hb) to drop. Foetal iron needs also begin to increase in trimester 2, contributing further to a decrease in your iron stores.

Something else happens in trimester 2 called hepcidin suppression. Hepcidin is a protein that regulates how much iron is absorbed from foods and supplements, typically hepcidin only allows you to absorb around 50% of iron consumed however in trimester 2 your body begins to suppress hepcidin in order to support increase foetal and maternal requirements for iron. The net effect however is still a decrease in iron.

The average ferritin level in trimester 2 is between 20 – 30 ug/L.

What happens in trimester 3?

By the time you get to trimester 3 (weeks 27 – 40) your iron stores might look even worse then they did in trimester 2, due to foetal iron requirements going from 3mg/day in trimester 2 to 7mg/day in trimester 3. Your hepcidin levels will be continually suppressed, allowing you to pick up more iron from food and supplement sources.

What is key to understand is that it’s not appropriate to expect women to maintain their iron levels throughout pregnancy. There is possibly a mis-match between the research that shows most women will move into a state of physiological anaemia during trimester 2 and 3, which is normal and our standard of care which is screening women for iron deficiency in trimester 2, when their iron is not expected to look good.

Reference ranges preconception and across the trimesters

Preconception

• Ideally your ferritin levels will sit around 50 ug/L, this is a a wonderful pro-active and preventative range to work toward if you have time.

Trimester 1

• If you have been able to allocate 3-6 months preconception you can maintain your ferritin levels of 50 ug/L.
• Women with ferritin levels over 30 ug/L are shown to carry much lower risk of requiring IV iron interventions later in pregnancy.
• Women with ferritin levels under 30 ug/L have a 50% chance of requiring IV iron interventions as a result of developing iron deficiency anaemia (IDA) later in pregnancy.

Trimester 2

• Average ferritin levels during trimester 2 are between 20-30 ug/L; our standard reference ranges are set at a minimum 30 ug/L.

Trimester 3

• Average ferritin levels during trimester 3 are 20 ug/L.

At any stage ferritin levels under 15 ug/L require attention and possible intervention.

What I recommend to my clients

I promote a proactive approach, which ideally does involve a preconception period in which we strategically work toward achieving a ferritin of 50 ug/L.

Not everyone has accounted for a preconception period, and that’s okay too. I do recommend blood testing as soon as possible in trimester 1, so that a strategic plan can be developed to improve your iron status prior to haemodilution occurring and foetal needs increasing in trimester 2.

Furthermore I recommend repeat testing at 8 week intervals throughout pregnancy, so that your ferritin levels along with other markers such as haemoglobin, transferrin, iron and transferrin saturation can all be monitored. This approach gives my clients the best chance at avoiding iron interventions later in pregnancy.

If you have been struggling with your iron levels, then the next step is booking in a complimentary consultation in which we will discuss your health challenges, health goals & what’s needed to get you there!

References

1. Crispin, P., Stephens, B., McArthur, E., & Sethna, F. (2019). First trimester ferritin screening for pre-delivery anaemia as a patient blood management strategy. Transfusion and apheresis science : official journal of the World Apheresis Association : official journal of the European Society for Haemapheresis, 58(1), 50–57. https://doi.org/10.1016/j.transci.2018.11.009
2. Khambalia, A. Z., Aimone, A., Nagubandi, P., Roberts, C. L., McElduff, A., Morris, J. M., Powell, K. L., Tasevski, V., & Nassar, N. (2016). High maternal iron status, dietary iron intake and iron supplement use in pregnancy and risk of gestational diabetes mellitus: a prospective study and systematic review. Diabetic medicine : a journal of the British Diabetic Association, 33(9), 1211–1221. https://doi.org/10.1111/dme.13056
3. Næss-Andresen, M. L., Eggemoen, Å. R., Berg, J. P., Falk, R. S., & Jenum, A. K. (2019). Serum ferritin, soluble transferrin receptor, and total body iron for the detection of iron deficiency in early pregnancy: a multiethnic population-based study with low use of iron supplements. The American journal of clinical nutrition, 109(3), 566–575. https://doi.org/10.1093/ajcn/nqy366
4. Daru, J., Allotey, J., Peña-Rosas, J. P., & Khan, K. S. (2017). Serum ferritin thresholds for the diagnosis of iron deficiency in pregnancy: a systematic review. Transfusion medicine (Oxford, England), 27(3), 167–174. https://doi.org/10.1111/tme.12408
5. Fisher, A. L., & Nemeth, E. (2017). Iron homeostasis during pregnancy. The American journal of clinical nutrition, 106(Suppl 6), 1567S–1574S. https://doi.org/10.3945/ajcn.117.155812
6. Klajnbard, A., Szecsi, P. B., Colov, N. P., Andersen, M. R., Jørgensen, M., Bjørngaard, B., Barfoed, A., Haahr, K., & Stender, S. (2010). Laboratory reference intervals during pregnancy, delivery and the early postpartum period. Clinical chemistry and laboratory medicine, 48(2), 237–248. https://doi.org/10.1515/CCLM.2010.033