Piperacillin/tazobactam is a bacteriolytic combined antibiotic. The least common reported adverse reactions of piperacillin/tazobactam are haematological reactions (<1%). The use of piperacillin/tazobactam during pregnancy is considered to be moderately safe (pregnancy category B) for the human embryo-foetus. This is a case of a pregnant patient (22 weeks of gestation) who was admitted to the Women’s Hospital, Doha, Qatar and was treated for preterm premature rupture of membrane with erythromycin for 10 days. Afterwards, she was treated with piperacillin/tazobactam for asymptomatic urinary tract infection (pseudomonas species). After 15 days, she developed fever, leucopenia, neutropenia and thrombocytopenia. These adverse reactions were reversed after the discontinuation of piperacillin/tazobactam combination. In Qatar and worldwide, there are few reported cases regarding bone marrow suppression or fever induced by piperacillin/tazobactam in general and during pregnancy. Using the Naranjo Adverse Drug Reaction Probability scales, the score was found to be 8, representing a probable adverse drug reaction.