This study aimed to describe the maternal-fetal attachment before and after obstetric bidimensional (US2D) and tridimensional (US3D) ultrasound and to compare the bond established following the exams performed. Fifty primigravidas were interviewed before and after US2D e US3D. The maternal-fetal attachment was improved after US2D o US3D (72%). Ninety percent of pregnant women expressed that the fetal image was better in the US3D than US2D. The women with ambivalent bond (16% US2D) or negative bond (24% US2D) changed this feeling immediately after perceive the fetal image at ultrasound exam. In conclusion, the ultrasound improves the maternal-fetal attachment independently of type of ultrasound performed.