Problem solving: Approach to a pregnant woman with anaemia

Disclaimer: This article is primarily intended for my students. However, the content is of a general nature, and may be of use to others as well.

Background Information:

One of the problem-solving questions in the theory examination concerns management of a pregnant woman with anaemia. Generally, anaemia in pregnancy refers to iron-deficiency anaemia (IDA), unless other causes are suggested in the question (like haemorrhage, for instance).

This article will focus on the management of iron-deficiency anaemia in pregnancy.

There are several dietary sources of iron. These may be heme or non-heme sources:

Heme iron

Liver
Red meat
Seafood
Poultry

Non-Heme iron

Beans
Dark green leafy vegetables
Dried fruit, raisins, apricots
Iron fortified cereals, bread

Patients must be advised to consume adequate iron in diet from the sources listed above.

During pregnancy, women receive iron and folic acid (IFA) supplementation. There may be a failure to respond to oral iron therapy due to any of the reasons listed below:

Inadequate iron intake (non-adherence, inadequate iron in supplement)
Inadequate iron absorption (concomitant consumption of items that inhibit iron absorption (tea, calcium), inadequate gastric acid secretion (use of proton pump inhibitors), malabsorption)
Ongoing blood loss (occult blood loss)
Coexisting condition interfering with bone marrow response (concomitant vitamin B12 or folate deficiency, bone marrow conditions)
Incorrect diagnosis (Haemoglobinopathy, anaemia of chronic disease or renal failure)

Intramuscular Iron injections have been effectively replaced by intravenous iron preparations because of the inconvenience of painful injection, dark discoloration of the skin, and the risk of myalgias, arthritis, hypersensitivity, lymphadenopathy. Low molecular weight iron dextran is the only preparation which can be recommended for intramuscular use in primary care settings with a Z technique if resuscitation facilities are available. However, the National guidelines for IDA continue to recommend IM iron for management of moderate IDA in pregnancy.

Among the iron studies, serum ferritin is the most sensitive and specific test for evaluating a patient’s iron stores. A serum ferritin of less than 30 microgram/L is diagnostic of iron deficiency and should prompt investigation for an underlying cause and appropriate treatment.

Diagnosing iron deficiency can be challenging as ferritin is also an acute-phase protein, which can be elevated in the presence of infections, autoimmunity, chronic kidney disease and certain malignancies. In these scenarios ferritin can potentially overestimate the patient’s iron stores. Serum ferritin up to 300 microgram/L can still be compatible with iron deficiency in the presence of inflammation and needs to be interpreted with other parameters measured in the iron profile and supportive red-cell indices such as mean corpuscular volume and a blood film (smear).

Transferrin is a protein that transports iron and reflects total iron-binding capacity. A transferrin saturation of less than 16% indicates an iron supply that is insufficient to support normal erythropoiesis.

Key Messages:

Approximately 60% of pregnant women in India have iron-deficiency anaemia (IDA).

The general approach to a question pertaining to IDA in pregnancy requires consideration of the following:

The severity of anaemia (Hb level)
The presence haemodynamic compromise/ cardiac failure/ ongoing blood loss
The period of gestation
Response to previous oral iron therapy (if administered)

The severity of anaemia (Hb level)

As one of the basic and universal investigations during pregnancy, one will typically be informed the Hb level. This must be used to classify the severity of anaemia. Management differs by severity- Hb <4 g/dl is an indication for urgent blood transfusion, but blood products may be avoided in case of moderate anaemia.

The presence of haemodynamic instability/ ongoing blood loss/ cardiac failure

In the presence of ongoing blood loss and/ or haemodynamic instability, urgent blood transfusion is indicated. Cardiac failure requires careful blood transfusion (if Hb <4 g/dl), usually with packed RBCs instead of whole blood.

The period of gestation

Following initiation of oral iron therapy, a rise in Hb of 1g/dl after 2 weeks, and 2g/dl after 4 weeks is expected. Thus, in patients with moderate IDA in 1st or 2nd trimester, one may be able to normalize Hb levels with the exclusive administration of oral iron. However, closer to term gestation, one doesn’t have the luxury of time, and must consider approaches that will raise Hb levels rapidly- IV iron preparations, blood products. Similarly, around term gestation, patients with severe anaemia will have to be counselled and referred for delivery at a health care facility with blood transfusion facility.

Response to previous oral iron therapy

Studies indicate that only one-third of women advised oral iron therapy for IDA in pregnancy adhere to treatment. The majority are non-compliant for a variety of reasons. Regardless, one must investigate all instances of failure to oral iron therapy to determine eligibility for parenteral iron therapy.

Indications and contraindications for IV iron therapy

The broad approach to a pregnant woman with IDA is given in the figure below. Please note that the algorithm prioritizes severity of anaemia over other considerations. Therefore, the management of severe anaemia is presented before moderate anaemia. Further, the algorithm excludes mention of IM iron preparations in contrast to national guidelines.

Answers to questions on IDA in pregnancy must factor the points mentioned above, and be suitably modified.

Note: IV iron preparations are clearly superior to oral iron preparations in their ability to raise ferritin and Hb levels (Following a single dose of Ferric carboxymaltose (FCM), serum ferritin levels will rise in 7-9 days; a greater proportion of women receiving FCM experience meaningful elevation of Hb levels (at least 1 g/dl) than women receiving oral iron preparations). However, they are expensive (500 mg injection of Ferric carboxymaltose costs between ₹2000 – 3000 on average).