Introduction

Pernicious anaemia is a type of autoimmune disease that is quite rare today, occurring in less than 1% of people of European descent.¹ It is often associated with reduced vitamin B12 (Cobalamin) absorption and other dietary abnormalities, which can result in a megaloblastic, macrocytic anaemia. It can be a challenge to diagnose the condition due to its large range of symptoms, and it can be detrimental to women of childbearing age and their unborn children. It is crucial to understand the role that vitamins, particularly B12, play in female obstetric health to prepare them for their pregnancy journeys adequately and ensure that the correct nutrients are provided to their children for growth and development.

Understanding pernicious anaemia

In a healthy individual, the stomach has specialised cells within the lining called parietal cells that produce intrinsic factor, a hormone involved in the transport of vitamin B12.² Vitamin B12 has a crucial role in maintaining a healthy lifestyle and is mainly obtained from the diet. Animal-based products (meat, fish and eggs) are the only way to increase circulating levels of the vitamin in the body without supplementing with oral or intramuscular (IM) sources.³

The most common cause of pernicious anaemia is autoimmune destruction of the parietal cells in the stomach. Often, people diagnosed with pernicious anaemia have other autoimmune conditions alongside, such as type 1 diabetes and Hashimoto’s thyroiditis.¹ Other risk factors for developing pernicious anaemia or vitamin B12 deficiency include having H. pylori bacterial infection of the stomach, proton pump inhibitor (PPI) medication usage and diets lacking in animal products like vegetarianism and veganism.⁴

Although anaemia is included in the name of the condition, it is important to note that people with pernicious anaemia may not present with altered haemoglobin levels in their blood tests. Particularly in females, unexplained iron deficiency anaemia (IDA) can be one of the first indicators of pernicious anaemia and needs further investigation by medical professionals.² Many tests can be used to determine the correct diagnosis, including both invasive and non-invasive techniques. Typically, blood tests will be done to check for any low haemoglobin and vitamin B12 levels of less than 148 pmol/L, which are needed to diagnose the condition. Blood smears can be used to check for the most common subtype of anaemia seen with pernicious anaemia, megaloblastic anaemia. Sometimes, a camera test into the stomach (gastroscopy) may be completed to check for atrophy of the stomach lining, which may be a sign of autoimmune gastritis.⁵ Testing for the H. pylori bacteria can also be done with a stool sample if suspected.

Maternal complications

Pernicious anaemia typically affects people aged 60-70 years, but can be seen in people over the age of 30 years too. The condition is rare today, but it’s more common in people with nutrient absorption issues or in areas with limited access to balanced meals. 

A wide range of symptoms can be seen in the condition, including:

• Memory loss and brain fog
• Pins and needles
• Mood swings
• Anxiety and depression
• Pallor, fatigue and light-headedness⁶

The most common cause of pernicious anaemia in pregnant people is a lack of nutrients, commonly due to vegetarianism/veganism. The demand for nutrients increases dramatically during pregnancy as both the foetus and the mother require increased quantities of vitamins and minerals. Additionally, during pregnancy, there is a gradual fall in B12 levels of around 30% by the third trimester. It is therefore recommended that pregnant or lactating women should take oral vitamin B12 supplements daily if they have any of the risk factors for vitamin deficiency.⁷

Having a vitamin B12 deficiency whilst pregnant can be detrimental to both the mother and baby. Studies worldwide have shown that a pregnancy-related deficiency can be associated with a higher risk of neural tube defect development in the foetus.⁸ In addition to this, women can experience increased incidence of pregnancy loss, preterm delivery and spontaneous abortion if the deficiency isn’t treated appropriately.⁹

Fetal complications

During pregnancy, the foetus has to obtain all of their nutrients from the mother’s diet. If the diet does not meet the recommended nutrient intake regularly, or the mother doesn’t have vitamin supplements, then the foetus will not fully grow and develop as is normally expected. Sometimes, the fetus can be a small for gestational age (SGA) baby, determined on regular growth scans and checkups and can be born with very low birth weights.⁹ Infants born to mothers with lower vitamin levels often suffer from growth restrictions, anaemia and major developmental abnormalities. 

In the postpartum period, lower maternal B12 levels can manifest in many different ways in the child. Many studies based on Indian and South Asian populations have shown that some children go on to develop insulin resistance and early-onset diabetes.¹⁰ Moreover, in severe and prolonged maternal deficiencies, a variety of features can become apparent in the child. These include psychomotor agitation, reduced neurological development and growth retardation.¹¹

A summary of foetal complications associated with pernicious anaemia in pregnancy are:

• Abnormal growth and development
• Insulin resistance
• Low birth weights
• Psychomotor agitation
• Anaemia

Treatment and future prevention

The mainstay of treatment for vitamin B12 deficiency is replacement of the vitamin either orally or via intramuscular injection (IM). The treatment regimen depends on the neurological signs of vitamin deficiency in mothers. If there are no neurological changes, then the regimen requires 3 doses of IM vitamin B12 for the first 2 weeks of treatment. This changes to IM injections every alternate day if there are neurological changes until there is improvement in symptoms.¹² In a diagnosis of pernicious anaemia, maintenance injections are needed for at least 2-3 months, and in cases where people prefer oral supplements, a short course of oral B12 1000 micrograms per day can be given. After 2 months postpartum, B12 levels are tested to confirm they have returned to normal if this treatment has been received during pregnancy.⁷

The key to preventing vitamin B12 deficiency or pernicious anaemia is maintaining a varied and balanced diet. Understandably, some people choose to avoid animal-based products and want to pursue vegetarianism/veganism. However, they must know the potential risks that come with this lifestyle and look into ways of supplementing essential vitamins and minerals. It is more difficult to tackle these issues in some of the more deprived areas of the world where access to a wide range of food, healthcare and education is less readily available. Patient education is imperative if we want to prevent further diagnosis of pernicious anaemia and vitamin deficiencies.

FAQs

What are the symptoms of Pernicious Anaemia?

There is a range of symptoms that Pernicious Anaemia can present with, affecting multiple body systems. Most common ones include diarrhoea, constipation, fatigue, jaundice and shortness of breath. More serious symptoms associated with vitamin B12 deficiency can include confusion, numbness, loss of concentration and depression.

What treatment is needed for vitamin B12 deficiency and Pernicious Anaemia for pregnant people?

There are no specific UK guidelines on how to treat a deficiency in pregnancy. However, doctors who specialise in the blood (haematologists) can offer help and advice to those prescribing. IM doses of vitamin B12 are thought to be best when treating deficient pregnant women, but women can opt to take oral versions of at least 1 mg per day if they prefer.

Summary

Pernicious anaemia is relatively rare in the present day due to the wide range of education, testing and knowledge that we now have. Maternal B12 deficiency is, however, a public health issue that needs to be tackled to reduce the adverse effects on the growing population. Not only does this condition have massive effects on the mother’s physical and mental health, but it can also be detrimental to the foetus as they develop and grow. The importance of B12 in the diet needs to be stressed to people from early on to prevent these issues from occurring too late in pregnancy. Further research needs to be undertaken to further explore the perinatal and postnatal risks that are associated with pernicious anaemia and especially B12 deficiencies globally.