To minimise irrational use of antibiotics by implementing guidelines for antibiotic usage in obstetrics and Gynaeocology.The observational study was conducted from January to December 2010 at the maternity unit of Aga Khan Hospital for Women and children, Kharadar, a secondary care facility in Karachi, Pakistan. Data was collected from medical records related to the study period. Prophylactic antibiotics were given according to the American College of Obstetricians and Gynaecologists recommendation 2009. Surveillance was done by surgical site infection rates and infectious morbidity. Data was analysed on SPSS 13.Therapeutic antibiotic use was rationalized, reducing the use of therapeutic antibiotics from 97% (n = 160/165) in January 2010 to 8% (n = 10/125) in December 2010. Surgical site infection rates were less than 5%. Cost of antibiotics per patient decreased by 90%. Decrease in the length of stay and workload on nursing staff was also observed.Implementing guidelines for antibiotic use in obstetrics and gynaecology and translating it into our protocols was effective in decreasing the irrational antibiotic consumption and increasing the rational use of antibiotics in the hospital.