No information is currently available on the safety of the aminoglycoside ribostamycin in pregnancy. We aimed to study the pregnancy outcome of women inadvertently exposed to ribostamycin during the first trimester of pregnancy. In a prospective cohort study, 102 women inadvertently exposed to ribostamycin during the first trimester of pregnancy and an age- and gravidity-matched control group, were enrolled. Study outcomes were gestational age at birth, major and minor malformations, and birth weight. Fetal outcomes were evaluated in 85 women inadvertently exposed to ribostamycin during the first-trimester of pregnancy and in 170 control subjects. Newborns were clinically examined at birth by a neonatologist and by imaging studies if any suspicious abnormalities were noted. There were 4/85 (4.9%) babies born with major malformations in the exposed group and 3/170 (1.8%) in the control group (P=0.7). Gestational age at delivery, rate of minor anomalies, rate of preterm births, and birth weight were not different between groups. In conclusion, similar to what is reported for other aminoglycoside, exposure to ribostamycin during the first-trimester of pregnancy does not appear to increase the risk of adverse fetal outcomes.