['Methotrexate (MTX) resistance is defined on the basis of the human chorionic gonadotropin (hCG) curve. The aim of this study was to identify low-risk non-metastatic patients with gestational trophoblastic neoplasia (GTN) who can achieve resolution by continuing MTX treatment despite a transient hCG plateau.', 'Before starting chemotherapy, 24 patients with FIGO Stage I GTN underwent transvaginal ultrasonography with power Doppler in order to identify myometrial lesions (areas of increased echogenicity and increased power Doppler signal). Ultrasound response to chemotherapy was defined when myometrial lesions decreased in echogenicity, Doppler signal or size. When ultrasound response occurred, despite chemoresistance defined by hCG values, MTX treatment was continued.', 'MTX was continued in three out of seven chemoresistant patients because ultrasound suggested response to MTX. All three of these patients achieved a complete response, thus nearly halving the MTX-resistance rate.'] Does transvaginal ultrasound predict delayed response to chemotherapy and drug resistance in stage I low-risk trophoblastic neoplasia?