Introduction
Worldwide, iron deficiency is the most common nutritional deficiency(1,2). Approximately 20% of pregnant women worldwide suffer from anaemia due to this(3).
During pregnancy, iron deficiency risk increases due to the requirement of additional iron to sustain the expansion of red cell mass, and the growth of the fetus and placenta(1). Iron deficiency contributes to adverse pregnancy outcomes such as intrauterine growth retardation and perinatal death(4,2). Some studies have shown maternal iron deficiency at delivery to be associated with lower serum ferritin levels in the cord blood of neonates, especially when the mother’s serum ferritin level was below 13 μg/l(5,6,7). This perhaps explains why iron deficiency impacts fetal and infant well-being by affecting brain development, auditory neural maturation, and increasing the risk of poorer cognitive, motor, social-emotional, and neurophysiologic development(4,8,9).
Iron deficiency is progressive: iron stores in the body gradually diminish, resulting in iron deficiency anaemia (IDA)(5,10). Latent iron deficiency (LID) occurs when iron stores are exhausted but the blood haemoglobin (Hb) levels are within normal limits(11). Hence women with LID are at a higher risk of developing IDA – associated with pregnancy complications, if not for early detection and treatment.
Assessment of Hb level alone, however, is not adequate to identify LID(12). Estimation of serum ferritin is the more pertinent method to detect body iron stores(5,13),(5). A serum ferritin level of <30 ug/l in pregnancy is considered as LID(5). Even though serum ferritin is currently available in most general hospitals in Sri Lanka, it is an expensive test and is not performed routinely. Therefore, surrogate screening tests are needed to identify women with LID.
In LID, the mean corpuscular volume (MCV) usually remains within normal limits, but a few microcytes may be detected on a blood smear(14). Therefore, increased red cell distribution width (RDW) may be an early indicator for LID(15,16). Red cell indices and RDW are low-cost investigations included in the full blood count (FBC), which can be undertaken in hospitals in Sri Lanka and other developing countries.
The prevalence of LID among pregnant women in Sri Lanka is currently not well known. Better awareness would enable clinicians to act within the routine antenatal care plan. Thus, the primary objective of this study was to assess the prevalence of LID in early pregnancy. Furthermore, the secondary objective was to identify LID using red cell indices, RDW, and blood films as surrogate screening tools.