OBJECTIVE: To study the effect of growth hormone (GH) treatment on ovarian and uterine morphology and function in short, prepubertal small-for-gestational-age (SGA) girls.DESIGN: A multinational, randomized controlled trial on safety and efficacy of GH therapy in short, prepubertal children born SGA.SETTING: Not applicable.PATIENT(S): A subgroup of 18 Danish girls born SGA included in North European SGA Study (NESGAS).INTERVENTION(S): One year of GH treatment (67 μg/kg/day) followed by 2 years of randomized GH treatment (67 μg/kg/day, 35 μg/kg/day, or IGF-I titrated).MAIN OUTCOME MEASURE(S): Data on anthropometrics, reproductive hormones, and ultrasonographic examination of the internal genitalia were collected during 36 months of GH treatment.RESULT(S): Uterine and ovarian volume increased significantly during 3 years of treatment (64% and 110%, respectively) but remained low within normal reference ranges. Ovarian follicles became visible in 58% after 1 year compared with 28% before GH therapy. Anti-Müllerian hormone increased significantly during the 3 years of GH therapy but remained within the normal range. Precocious puberty was observed in one girl; another girl developed multicystic ovaries.CONCLUSION(S): GH treatment was associated with statistically significant growth of the internal genitalia, but remained within the normal range. As altered pubertal development and ovarian morphology were found in 2 of 18 girls, monitoring of puberty and ovarian function during GH therapy in SGA girls is prudent. Altogether, the findings are reassuring. However, long-term effects of GH treatment on adult reproductive function remain unknown.CLINICAL TRIAL REGISTRATION NUMBER: EudraCT 2005-001507-19.