Ultrasound (US) is the preferred imaging method to assess in the evaluation of obstetrics pathology, which continues to be cheaper and accessible compared to magnetic resonance imaging (MRI). Despite it is low specificity, US has demonstrated to be high sensitivity for diagnosing the main maternal-fetal conditions and to be superior to MRI especially when US uses high resolution techniques, tridimensional reconstruction or Doppler for an accurate hemodynamic detail of fetal heart. Nevertheless, MRI is the preferred exam for CNS assessment, fetal malformations and other conditions difficult to evaluate through US. The present work reviews the technique, indications, risks and special considerations about MRI use in obstetrics.