In 1958 Kass (1) was the first to present evidence that asymptomatic bacteriuria is apparent in 6 to 7% of all pregnant women during their first prenatal visit. Kass observed that low birth weight, prematurity and increased prenatal mortality are associated with asymptomatic bacteriuria. Others suggested that the urinary bacteria might be transmitted to the unborn baby and cause fetal septicemia. Maternal pyelonephritis, a serious obstetric condition, is described in 2 to 4% of all pregnant women, mainly following asymptomatic bacteriuria. Evidently, urinary tract infection (UTI) and asymptomatic bacteriuria should be prevented in pregnancy. Nitrofurantoin is largely used for these indications in nonpregnant women due to its exceptional effectiveness and low rate of adverse effects. However, to allow its safe use during pregnancy, it is crucial to address its reproductive safety. To date, despite scores of studies showing its efficacy in eradicating UTI in pregnant women, nitrofurantoin's safety has not yet been determined. In order to address this issue we reviewed all published literature that examined the safety of nitrofurantoin in pregnancy and performed meta-analysis of all eligible studies. The objective of our study was to determine whether a relationship exists between maternal ingestion of nitrofurantoin during pregnancy and a subsequent increased rate of malformation.