Iron status in relation to morbidity when considering iron supplementation among urban pregnant women in South Africa

Abstract

Background: Anaemia is a common and challenging nutritional problem worldwide and iron deficiency (ID) contributes to about half of all anaemia. In 2002, ID anaemia was considered to be one of the most important contributing factors to the global burden of disease. The prevalence of anaemia in South Africans older than 15 years of age is 17.5%. During pregnancy it is especially important to prevent anaemia and ID. In an attempt to do this, various countries provide routine iron supplementation to pregnant women. These supplementation regimes are not homogenous worldwide and may not be appropriate for iron replete women. In South Africa (SA), a standard quantity of ~60 mg of elemental iron is provided daily to all pregnant women, regardless of a large proportion of them being iron-sufficient. These women may experience a greater incidence of adverse effects due to excess iron intake or a high iron status. These adverse effects include hypertension, gestational diabetes mellitus (GDM), oxidative stress, decreased zinc absorption and increased infectious morbidity. Furthermore, these adverse effects may be modulated by n-3 polyunsaturated fatty acid (PUFA) status. Aim: The overall aim of this dissertation was to assess whether iron status and anaemia at < 18 weeks of gestation is associated with morbidity during the course of pregnancy in urban pregnant women receiving routine iron supplementation in SA. More specifically, investigating associations with the incidence of morbidity symptoms, blood pressure and the incidence of hypertension, as well as blood glucose and the incidence of GDM during pregnancy. Furthermore, the association of morbidity symptoms and blood pressure with n-3 PUFA status, were also examined. Design: In a prospective observational analysis, pregnant women (at < 18 weeks of gestation) attending antenatal care facilities in selected clinics within the City of Johannesburg in SA, were recruited. The first phase data collection took place at Rahima Moosa Mother and Child Hospital along with further follow-up visits at 22 and 36 weeks of pregnancy, and birth. Morbidity symptoms were recorded by the women for the duration of pregnancy. Additionally, blood pressure, blood glucose and n-3 PUFA status were measured and compared between women with and without ID and anaemia, which were based on ferritin and haemoglobin concentrations respectively. Results: ID and anaemia prevalence among all women was 11.9% and 20.8%, respectively. Diastolic blood pressure was higher and mean arterial pressure tended to be higher in the iron-sufficient group at 36 weeks gestation, compared to the group with ID, when corrected for age, height, weight, ethnicity and n-3 PUFA status (p = 0.045 and p = 0.075, respectively). Morbidity symptoms, namely fever, extreme tiredness, coughing and diarrhoea were higher in the iron-sufficient group than the ID group between 18 and 40 weeks gestation (p < 0.001, p = 0.043, p < 0.001 and p = 0.014, respectively). Between 18 and 40 weeks, extreme tiredness, runny nose and diarrhoea were higher in the anaemic group (p = 0.031, p = 0.010 and p = 0.024, respectively) than in the non-anaemic group. Also in this duration, women who were compliant to iron supplementation had a higher incidence of fever, extreme tiredness, runny nose and vomiting (p < 0.001, p = 0.013, p = 0.025, p = 0.008, respectively) compared to the iron non-compliant women. Throughout pregnancy, women with a higher n-3 PUFA status, experienced a lower incidence of fever, extreme tiredness, headache, runny nose, coughing, diarrhoea, vomiting, constipation and heartburn (p < 0.001, p < 0.001, p < 0.001, p < 0.001, p = 0.018, p = 0.008, p = 0.045, p < 0.001 and p = 0.037, respectively). Conclusion: This study showed that iron-sufficient pregnant women receiving daily routine iron supplementation of ~60 mg elemental iron experienced a higher incidence of morbidity symptoms, including infectious morbidity symptoms. These women also had a higher diastolic blood pressure at 36 weeks gestation, which may increase the risk of hypertension. Our study, however, showed greater associations with morbidity in iron-sufficient women, than in non-anaemic women. This indicated that iron sufficiency should be evaluated when providing iron supplementation to pregnant women. Furthermore, women with an n-3 PUFA status above the median experienced less fever, extreme tiredness, headache, runny nose, coughing, diarrhoea, vomiting, constipation and heartburn during pregnancy, compared to women with an n-3 PUFA status below the median. It may be important to re-evaluate the iron supplementation strategy during pregnancy in SA.