Iron Deficiency in Women’s Health
Iron deficiency is one of the most common nutritional deficiencies in the world, and is the only nutrient deficiency that is significantly prevalent in almost all industrialized countries.
Women are at particular risk of iron deficiency due to blood loss during menstruation and the increased demand for iron during pregnancy.2 This is reflected in incidence rates for iron deficiency. For example, in the UK, 21% of female teenagers between 11 and 18 years, and 18% of women between 16 and 64 years are iron deficient.2
Prevalence of iron deficiency (%) in women by age3
Figure 1: Prevalence of iron deficiency in women of different ages in the United States
The chart above shows data from the large, National Health and Nutrition Examination Survey (NHANES III) in the US. In comparison to the relatively high prevalence of iron deficiency in women, the study recorded a prevalence of iron deficiency of only 1% in men < 50 years old.3
Other factors that have been shown to increase the risk of iron deficiency in women include:
- Use of an intrauterine device (IUD)2
- High parity2
- Vegetarian diet2
- Growth spurt during teenage years2
- Intensive exercise5
Women are also at greater risk of experiencing fatigue and exhaustion, and are three times more likely than men to present with fatigue symptoms in general practice.6 Fatigue and exhaustion can be symptoms of iron deficiency.7 Fatigue is different to tiredness.
Menstruation is, in itself, a risk factor for iron deficiency,2 with heavy menstrual bleeding (HMB) the most common cause of iron deficiency anaemia in the developed world.8 Some studies suggest that up to 30% of women of reproductive age are afflicted with HMB.8
HMB can be defined as blood loss during menstruation of more than 80 ml2 (median loss is 30 ml4), although some definitions do not specify a specific threshold for blood loss. For example the UK NICE guidelines define HMB as ‘excessive menstrual blood loss which interferes with a woman’s physical, social, emotional and/or material quality of life’.9
Because every ml of blood lost translates into a 0∙5 MG loss of iron, menstruation, particularly HMB, increases the risk of iron deficiency.2 Another factor impacting upon iron stores is the duration of menstruation. Depleted iron stores are seen in 5% of women bleeding for less than 4 days, 11% in those who bleed for 4-6 days, and 20% in those bleeding for more than 6 days.4
Assessing blood loss is not practical for the patients, and teenage girls in particular may find it difficult to talk about. Some questions that may help gauge if menstrual bleeding is excessive include:
- Do you need to use double sanitary protection (tampons and towels)?
- Do you sometimes leak through your clothes or on to your bedding?
- Do you need to change your pad/tampon every two hours or more?
- Do you pass large blood clots (more than 1 inch across)?
Treating Iron Deficiency in HMB
Once HMB is diagnosed, it is important that the underlying cause is identified and treated, including the exclusion of endometrial cancer, atypical hyperplasia and any structural abnormalities.9 If no abnormalities are found, pharmaceutical treatments such as a levonorgestrel-releasing intrauterine system, tranexamic acid, NSAIDs or oral contraceptives,9 or surgical approaches such as endometrial ablation,9 could be considered.
Alongside the identification and treatment of the underlying cause of HMB, it is important to consider that the patient may have iron deficiency, and to treat it appropriately.10 Iron deficiency can cause fatigue, reduce work performance,2 and have a negative impact on the patient’s perception of their general health.11Treating iron deficiency anaemia has been shown to reduce patients’ feelings of fatigue and improve their quality of life.12
Pregnancy and postpartum
Iron deficiency anaemia in pregnancy can have serious consequences, including low birth weight and premature birth.13 Approximately 40% of women enter pregnancy with low or depleted iron stores, while 25% of pregnant women not taking iron supplements have iron deficiency anaemia.13
The iron status of the mother can also impact on the health of the infant after birth. In the last trimester the foetus accrues 80% of iron needed for its first 4-6 months of life.14 This iron is used for the growth and development of the hippocampus, as the gut is too immature to regulate absorption of iron until 6-9 months of age.15
If a mother is iron deficient during her pregnancy, in combination with blood loss at delivery, she is more likely to be anaemic postpartum.16 One study showed that 26% of women not taking iron supplements were iron deficient one week after a normal delivery.16,17 Iron deficiency postpartum is associated with an increased risk of depression,18 increased prevalence of infections,16 can cause fatigue19 and exhaustion, impacting upon the quality of breast milk produced,20 and ability to breast feed successfully.21
For more information on the importance of iron in pregnancy and postpartum see our dedicated section on “postpartum and pregnancy”.