Anaemia in pregnancy

It is a Wednesday morning and you are reviewing a 28-week booking blood on a woman who feels constantly tired. Her haemoglobin is 92 g/L, her mean cell volume is 76 fL, her ferritin is 9 micrograms per L. This is the second most common problem an obstetrician sees in clinic — the diagnosis is easy, the dose ladder is easy, and yet examiners find ways to fail it because candidates confuse physiological anaemia with iron deficiency, give iron the wrong way, or transfuse when they should have infused. This topic fixes all three.[1][9]

Overview and definition

Pregnancy lowers the haemoglobin concentration by design. Plasma volume rises around 40 to 50 percent by the third trimester, red cell mass rises only 20 to 30 percent — the result is a dilutional drop of roughly 10 g/L that is physiological, not pathological. The trap is treating it with iron. The second, more dangerous trap is missing true iron deficiency because the ferritin was not checked.[1][9]

The thresholds you quote:[1]

• First trimester: haemoglobin under 110 g/L.
• Second and third trimester: haemoglobin under 105 g/L.
• Postpartum: haemoglobin under 100 g/L.
• Severe anaemia: haemoglobin under 70 g/L — the threshold at which Daru's multilevel analysis showed a 2.36-fold adjusted odds ratio for maternal death (95 percent confidence interval 1.60 to 3.48).[2]

References14Show ledgerHide ledger

1. [1]American College of Obstetricians and Gynecologists Anemia in Pregnancy: ACOG Practice Bulletin, Number 233 Obstet Gynecol, 2021.PMID 34293770
2. [2]Daru J, Zamora J, Fernández-Félix BM, Vogel J, Oladapo OT, Morisaki N, Tunçalp Ö, Torloni MR, Mittal S, Jayaratne K, Lumbiganon P, Togoobaatar G, Thangaratinam S, Khan KS Risk of maternal mortality in women with severe anaemia during pregnancy and post partum: a multilevel analysis Lancet Glob Health, 2018.PMID 29571592
3. [3]Rogozińska E, Daru J, Nicolaides M, Amezcua-Prieto C, Robinson S, Wang R, Godolphin PJ, Saborido CM, Zamora J, Khan KS, Thangaratinam S Iron preparations for women of reproductive age with iron deficiency anaemia in pregnancy (FRIDA): a systematic review and network meta-analysis Lancet Haematol, 2021.PMID 34171281
4. [4]Peña-Rosas JP, De-Regil LM, Garcia-Casal MN, Dowswell T Daily oral iron supplementation during pregnancy Cochrane Database Syst Rev, 2015.PMID 26198451
5. [5]Breymann C, Milman N, Mezzacasa A, et al. Ferric carboxymaltose vs. oral iron in the treatment of pregnant women with iron deficiency anemia: an international, open-label, randomized controlled trial (FER-ASAP) J Perinat Med, 2017.PMID 27278921
6. [6]Khalafallah AA, Hyppa A, Chuang A, Hanna F, Wilson E, Kwok C, Yan C, Gray Z, Mathew R, Falloon P, Dennis A, Pavlov T, Allen JC A Prospective Randomised Controlled Trial of a Single Intravenous Infusion of Ferric Carboxymaltose vs Single Intravenous Iron Polymaltose or Daily Oral Ferrous Sulphate in the Treatment of Iron Deficiency Anaemia in Pregnancy Semin Hematol, 2018.PMID 30502851
7. [7]Froessler B, Schubert KO, Palm P, Church R, Aboustate N, Kelly TL, Dekker GA, Hodyl NA Testing equivalence of two doses of intravenous iron to treat iron deficiency in pregnancy: A randomised controlled trial BJOG, 2023.PMID 36047598
8. [8]Radhika AG, Sharma AK, Perumal V, Sinha A, Sriganesh V, Kulshreshtha V, Kriplani A Parenteral Versus Oral Iron for Treatment of Iron Deficiency Anaemia During Pregnancy and post-partum: A Systematic Review J Obstet Gynaecol India, 2019.PMID 30814805
9. [9]Camaschella C Iron deficiency Blood, 2019.PMID 30401704
10. [10]Markova V, Hansen R, Thomsen LL, Pinborg A, Moos T, Holm C Intravenous iron isomaltoside versus oral iron supplementation for treatment of iron deficiency in pregnancy: protocol for a randomised, comparative, open-label trial Trials, 2020.PMID 32843079
11. [11]Daniilidis A, Panteleris N, Vlachaki E, Breymann C, Assimakopoulos E Safety and efficacy of intravenous iron administration for uterine bleeding or postpartum anaemia: a narrative review J Obstet Gynaecol, 2018.PMID 29057687
12. [12]Oteng-Ntim E, Pavord S, Howard R, et al. Management of sickle cell disease in pregnancy. A British Society for Haematology Guideline Br J Haematol, 2021.PMID 34409598
13. [13]Chou ST, Alsawas M, Fasano RM, Field JJ, Hendrickson JE, Howard J, Kameka M, Kwiatkowski JL, Pirenne F, Shi PA, Stowell SR, Thein SL, Westhoff CM, Wong TE, Akl EA American Society of Hematology 2020 guidelines for sickle cell disease: transfusion support Blood Adv, 2020.PMID 31985807
14. [14]Drakesmith H, Pasricha SR, Cabantchik I, Hershko C, Weiss G, Girelli D, Stoffel N, Muckenthaler MU, Nemeth E, Camaschella C, Klenerman P, Zimmermann MB Vaccine efficacy and iron deficiency: an intertwined pair? Lancet Haematol, 2021.PMID 34450104