Role of Maternal Serum Ferritin in the Prediction of Low Neonatal Birth Weight

Intrauterine growth restriction (IUGR) is defined as fetal growth slower than the normal growth potential of a specific fetus because of genetic or environmental factors. IUGR is associated with a high incidence of perinatal morbidity and mortality. IUGR neonates have a greater risk of hypoxic ischemic encephalopathy, intraventricular hemorrhage and necrotizing enterocolitis with longer hospital stay and higher health care costs. Incidence of a fetus developing a small size for gestational age is about 8%. Fetal growth is regulated by the balance between fetal nutrient demand and maternal placental nutrient supply. Intrauterine growth restriction may be caused by maternal, placental, or fetal factors. Nearly one-third of IUGRs are due to genetic causes, and two-thirds are related to the fetal environment. In the developing world, IUGR is likely to be a consequence of poor maternal nutritional status prior to or during pregnancy.

There are two general patterns of growth abnormalities: symmetric and asymmetric. Symmetric growth inhibition arises during the first half of gestation, when fetal growth occurs primarily through cellular division and produces an undersized fetus with fewer cells of normal size. Asymmetric growth inhibition occurs during the second half of gestation and is usually the consequence of an inadequate availability of substrates for fetal metabolism. To prevent the previously mentioned complications of IUGR, it is important to establish markers which can identify pregnancies at risk of IUGR early enough. Recently several studies have highlighted the role of many bio-molecules as markers for IUGR like leptin, adiponectin, endothelin-1, lactate dehydrogenase, s-endoglin, pregnancy associated plasma protein, metastin. Apart from being expensive, laboratories at majority of centers are not equipped with facilities of measurement of these markers. Measurement of maternal serum ferritin has also been used as a predictive marker for increased risk of IUGR in one previous study on a limited number (seventeen) of cases. Ferritin is an intracellular protein consisting of 24 heavy and light sub-units surrounding a core that can store up to 4,500 iron atoms. The two sub-units are highly conserved during evolution, but only the heavy sub-unit has ferroxidase activity. Ferritin is released by infiltrating leukocytes, in response to acute and chronic infection. Ferritin as an acute phase reactant is well known for its intracellular iron sequestration and storage abilities during immune activation. Serum ferritin concentration is positively correlated with the amount of total body iron stores in the absence of inflammation. Serum ferritin is considered a valuable bio-marker for body iron status in healthy subjects.Iron deficiency has its known deleterious effect in pregnancy but iron loading may be associated with oxidative damage to cells and tissues. It has been shown in various studies that lower level of transferritin receptor expression in placenta is associated with preeclampsia and IUGR. This can lead to decrease extraction of iron by placenta from maternal serum leading to increase maternal serum ferritin. This fetal iron deficiency leads to increase in fetal corticotropins and fetal cortisol, causing inhibition of fetal growth.