8. Obstetric Anaemia

Maternal anaemia is a common condition.

According to the World Health Organization, pregnancy anaemia and postpartum anaemia is very frequent across the world, and confers a number of health risks to mother and child [1].

Maternal symptoms and signs include fatigue, paleness and cardiovascular strain, reduced mental and physical performance and increased risk for blood transfusion [2, 3]. Thyroid and immune functions may also be affected [2, 4].

The most frequent type of obstetric anaemia is iron deficiency anaemia (IDA), both worldwide and in developed countries, in spite of decades of guidelines and recommendations on prevention and treatment [1, 2, 5]. Iron is needed for many physiological processes in the body, and observational studies indicate that iron deficiency during pregnancy may independently cause cognitive or behavioural abnormalities in the child [6-8].

Other causes include other nutritional deficiencies, infectious diseases and genetic red cell disorders [9]. Peri- and postpartum haemorrhage may induce or aggravate anaemia postpartum. Prevention and treatment, especially iron is widely available, but not applied sufficiently. Severe anaemia may require transfusion, particularly if there is also a significant blood loss at delivery.

Why Is Obstetric Anaemia Important

Maternal deficiency of iron is by far the most frequent cause of obstetric anaemia
Maternal anaemia is frequent despite knowledge, guidelines and widely available treatment
Maternal anaemia is thought to be the most frequent cause of maternal death
Anaemia during pregnancy increases the risk of induction of labour or caesarean section
Anaemia during pregnancy increases the risk of postpartum anaemia
Pregnancy IDA (iron deficiency anemia) is linked to a number of harmful effects on the foetus, including intrauterine growth restriction, death in utero, infection, preterm delivery and neurodevelopmental damage, which may be irreversible [6-8, 10]
Failure to treat maternal IDA may carry over to the next pregnancy

Pregnancy Anaemia

From the sixth week of gestation

Hormones induce haemodynamic changes. Even though there is an increase in red cell mass, plasma volume increases relatively more [11]. Therefore, obstetric anaemia is defined by specific haemoglobin limits, which are lower than in non-pregnant women. The increased red cell production increases iron needs, which frequently leads to iron depletion, as women in the fertile age often have marginal iron stores [2].

Definitions of pregnancy anaemia differ:

WHO definition: Haemoglobin < 11 g/dL in first and last trimester, and < 10.5 g/dL in the second trimester [5]. BCSH guidelines: Haemoglobin < 11g/dL in first trimester, < 10.5 g/dL in second and third trimesters [12]

Mild anaemia during pregnancy

May not harm mother or child, but a haemoglobin level below 9 g/dL is associated with a 2-3 fold increased risk for intrauterine growth restriction, which in severe cases may lead to intrauterine foetal death [2].

Pregnancy IDA (Iron Deficiency Anemia)

is by far the most frequent type [9, 9, 13], and is seen in approximately 25% of pregnant women, even in highly industrialized countries, and ethnicity and age are strongly associated with anaemia prevalence [14, 15]. Prevalence of anaemia during pregnancy shows a large geographical variation caused by environmental, socio-economic and hereditary factors: Europe and North America 17-31%, South-East Asia 44-53% and Africa 53-61%. Approximately 20% of who have haemoglobin levels below 8/dL, and Iron deficiency is the most common cause, as the vast majority of women have iron stores too low to meet the cumulative needs of pregnancy and delivery [5, 5, 16].

Multiple other acquired aetiologies exist:

Folate deficiency, vitamin B12 deficiency, parasitic infestation (malaria, hookworm), bacterial infection, autoimmune haemolytic anaemia, toxic/aplastic anaemias, haematological malignancies and PNH [2, 9].

Diagnosis is essential

should be adapted to the geographic region due to the different treatment and prognosis. Clinical and laboratory investigation should at least look for iron and folate deficiency and rule out infection, malignancies and hereditary disorders [2, 17].

Prevention:

IDA can be prevented by taking 15-60 mg of iron diet daily [18] (or 2-3 times per week, which reduces the side effects [19]), though not all countries recommend this [17].

Other types of anaemia

Treatment should target the underlying disease or condition.

Blood transfusion

Carries a number of risks including volume overload and should only be used for acute bleeding, haematological conditions and severe cases of refractory anaemia, where low haemoglobin levels or insufficient physiological compensation are thought to cause an imminent risk for mother or foetus [17].

Treatment

For ID and manifest IDA higher dosage, between 65-200 mg of elemental iron is required [18]. This frequently induces significant gastro-intestinal side effects, resulting in low compliance rates: Inflammation and intestinal malfunction severely limits absorption. If oral iron is not feasible or effective, intravenous iron can induce repletion of iron stores within 1-2 days and normalisation of haemoglobin levels in 1-3 weeks, and can be used from the second. Trimester onwards, provided that blood and iron physiology is otherwise normal [12, 20].

Postpartum Anaemia

Definition:
Haemoglobin < 10 d/dL [17]

Prevalence:
If postpartum anaemia is defined as a Hb < 10 g/dL, the prevalence 30% or higher [17], if defined as < 11g/dL, the prevalence is up to 50%, with no iron intake during pregnancy. With routine intake of iron during pregnancy, postpartum anaemia has been recorded in 14% [21].

Aetiologies:
Postpartum haemorrhage alone or in combination with pregnancy iron deficiency is a common cause of postpartum anaemia. Other aetiologies: see pregnancy anaemia above.

Postpartum haemorrhage (PPH)
can be defined > 500 ml of blood loss within 24 hours after delivery [22]. PPH is seen in approximately 18% of all deliveries. Severe PPH, defined as blood loss of > 1000 ml, is seen in 4-5% of deliveries, and PPH > 2500 ml is seen in 0.4% of births [23, 24]. Normally 500 mg of iron is stored in the liver, corresponding to formation of the erythrocytes in 1 litre of blood. If the haemorrhage is severe or there is a pre-existing pregnancy ID or IDA, the blood loss at delivery will almost invariably lead to postpartum IDA.

Prevention:
Treating anaemia during pregnancy and managing obstetric haemorrhage reduces the risk of postpartum IDA, see pregnancy anaemia above, and guidelines for the management of obstetric haemorrhage [25].

Treatment

• The majority of obstetric anaemia cases can be prevented or treated based on their aetiology (e.g. by supplementing iron or folate or treating the underlying disease), if diagnosed in time. Oral iron supplementation is the gold standard for the treatment of IDA, and intravenous iron can be used where oral iron is not feasible or effective, from second trimester in pregnancy and onwards [26].

• Red cell transfusion is given in approximately 2% of all deliveries [27], and should be reserved for the treatment of major haemorrhage and severe anaemia with cardiac incompensation, where other treatment options are insufficient, as the clinical effect of red cell transfusion on common anaemia symptoms does not outweigh its risks and costs [28, 29]