Obstetrics and Gynaecology

Iron deficiency disproportionately affects women compared with men, and is particularly common in women of reproductive age.1 Iron deficiency is estimated to occur in approximately 9–11% of women aged 12–49 years in developed countries, with the rate dropping to 5% in women aged 50–69 years before increasing again in older women.2 Factors increasing the risk of iron deficiency in women include menstruation, pregnancy3 and peripartum blood loss.4

Menstrual blood loss is one of the primary causes of iron deficiency in non-pregnant, premenopausal women.5 The average menstrual blood loss of 35 mL over a cycle increases the daily iron requirement by 50–70% relative to the absence of menstruation.5 Menstrual blood loss may be considerably higher in adolescents experiencing anovulatory bleeding,6 in women using intrauterine contraceptive devices3 and in women at a late stage of reproduction.7

Chronic bleeding may also occur as a result of disease. In postmenopausal women, blood loss associated with gastrointestinal lesions or cancer is the most common cause of iron deficiency and may partly explain the rise in iron deficiency with age in the postmenopausal group.8

Heavy Menstrual Bleeding (HMB) can be defined as blood loss during menstruation of more than 80ml3 although some definitions do not specify a threshold for blood loss. 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 HMB is the leading cause of iron deficiency anaemia in the developed world.10

Pregnancy increases a woman’s iron needs 3-fold in order to support the growth of the fetal-placental unit and increased red-cell mass.3 Meeting this demand requires a diet high in bioavailable iron, but also stored iron levels of at least 300 mg before pregnancy.11 Unfortunately, approximately 40% of women enter pregnancy with low or absent iron stores, leading to around 25% of pregnant women in Western societies having iron deficiency anaemia.12

Women suffering from iron deficiency anaemia during the first two trimesters are twice as likely to deliver early, have three times the risk of having a low birth weight infant,13 and an increased risk of having an infant small for gestational age.12 Iron deficiency is also associated with negative outcomes, including increased risk of haemorrhage, maternal mortality and low birth weight.14

Peripartum blood loss can result in iron deficiency and anaemia, with a loss of more than 500 mL sufficient to cause anaemia in women without prior iron deficiency anaemia.6 The median blood loss during vaginal delivery is 250 mL, but blood loss in excess of 1000 mL occurs in more than 5% of deliveries,6 increasing the risk of postpartum anaemia 74-fold.4

Postpartum anaemia is associated with a range of consequences, including:

  • Increased risk of postnatal depression15
  • Increased prevalence of urinary tract infections16
  • Fatigue17
  • Insufficient milk syndrome18
  • Reduced breast milk quality19

Treating iron deficiency in women

In non-anaemic menstruating women with unexplained fatigue and ferritin levels below 50 μg/L, iron supplementation has been shown to result in a significant reduction in symptoms of fatigue, and improvements in biological markers, including haemoglobin.20

Treatment guidelines referring to iron deficiency in pregnancy recommend that all women be given dietary information to maximise iron intake and absorption. Iron supplementation may also be appropriate.21