WHO recommends antenatal deworming of pregnant women living in areas where the prevalence of helminthes infection exceeds 20-30%. However, mass deworming is not yet included in routine antenatal care protocols in Calabar and in many other countries. The prevalence of helminthes infection in Calabar was reported at 28.3% in previous study. In this study, presumptive treatment of pregnant women in their second trimester with oral Mebendazole (500mg), a broad-spectrum anthelmithic drug, was carried out. The aim of the study was to establish the impact of ante-natal deworming on the prevalence of peripartum anaemia in pregnancy. This was a placebo controlled study where 560 pregnant women in their second trimester were randomized to receiving single dose mebendazole (500mg) and placebo. They were followed-up to term and haemoglobin levels were determined pre-treatment and at term. Anaemia was considered for hemoglobin values of less than 11g/dl or Packed cell volume (PCV) of less than 33% according to WHO. The prevalence of anaemia in the treatment group was 12.6% compared with 29.9% in the placebo (p<0.001). Anaemia was recorded more among women with high parity (OR=5.063, 95% CI=1,531-16.743). Inclusion of anthelminthics in routine antenatal care programme can significantly improve maternal health.