BACKGROUND Anaemia in pregnancy is a global problem but it is more prevalent in the developing countries and is associated with increased maternal morbidity and mortality. Iron deficiency is the most common cause of anaemia in pregnancy.Inadequate iron intake can lead to varying degrees of deficiency;from low iron stores to early iron deficiency and iron deficiency anaemia.Serum ferritin is the single best non invasive test and is a very useful and reliable index of iron stores especially in pregnancy. OBJECTIVES This cross-sectional descriptive study was carried out to evaluate the serial serum ferritin and packed cell volume amongst antenatal women with iron deficiency in Irrua Specialist Teaching Hospital in determining their response to oral iron prophylaxis. METHODOLOGY A total of 345 pregnant women with iron deficiency were recruited as subjects in this study at first trimester within the age range of 17 and 41 years in Irrua Specialist Teaching Hospital. Peripheral venous blood were obtained at booking in first trimester,they were subsequently commenced on 200mg of ferrous sulphate at booking,then a repeat peripheral venous blood sampling was done between 24-26 weeks and 34-36 weeks.PCV was tested using microhaematocrit reader after centrifugation while serum ferritin was tested using ELIZA method.Data was analysed using SPSS version 16.0.Tables,charts and other statistical parameters were used to present the results.