产前影像学诊断包括产前胎儿超声和胎儿MRI，是出生缺陷二级防控的重要手段。胎儿MRI的优势为安全性高，迄今尚未发现3.0 T及以下MRI检查会对孕妇和胎儿造成任何不良后果；而且MRI以其软组织对比好、大视野、多方位及多参数成像，具有无辐射、非侵入性，不受孕妇肥胖体型、羊水量过少、胎头钙化等因素影响的特点，成为产前超声诊断中、晚孕期胎儿疑似结构异常的重要补充手段。胎儿MRI检查的目的是确认胎儿超声检查结果，或者胎儿超声怀疑胎儿结构异常，但是不能明确诊断时。由于胎儿MRI检查，可能获得比胎儿超声更多的信息，因此可弥补胎儿超声检查的不足。胎儿MRI的适应证包括：对产前超声检查怀疑胎儿中枢神经系统畸形、脑室扩张、脑中线结构异常、后颅窝增宽或小脑蚓部异常等，唇裂是否合并腭裂或牙槽骨异常，胎儿耳廓畸形是否合并外耳道闭锁或中耳、内耳发育不良，怀疑胎儿心外大血管畸形的进一步确诊，对胎儿腹、盆部肿块定位及定性，对胎儿肠道畸形、泌尿道生殖道畸形及单绒毛双胎并发症，对胎儿疾病治疗前、后疗效进行评价及对预后与严重疾病终止妊娠前进行评估等。胎儿MRI检查结果可为产前诊断、优生优育及遗传咨询提供相关信息，为胎儿疾病治疗方案制定、分娩方式选择及医患沟通提供依据。尽管胎儿MRI可以对胎儿解剖进行标准及完整的评估，但是仍然不作为产前影像学诊断的首选。

Prenatal imaging diagnosis includes prenatal fetal ultrasound and fetal MRI, which is an important means of secondary prevention and control of birth defects. The advantage of fetal MRI is safe, and so far, it has not been found that MRI examination of 3.0 T or below will bring any adverse consequences to pregnant women and fetuses. MRI has become an important supplementary means for prenatal ultrasound diagnosis of fetal structural abnormalities in the second and third trimester of pregnancy, because of good soft tissue contrast, wide field of vision, multi-orientation and multi-parameter imaging, and advantages of non-radiation and non-invasion, and not affected by factors such as maternal obesity, oligohydramnios, and fetal head calcification. The purpose of fetal MRI examination is to confirm results of prenatal ultrasound examination, or when an abnormality is suspected by prenatal ultrasound without a definitive diagnosis. MRI examination may obtain more information from fetus than prenatal ultrasound, and make up for some deficiencies of prenatal ultrasound. Indications of fetal MRI include central nervous system congenital malformations suspected of fetus by prenatal ultrasound examination, ventricular dilatation, brain midline structural abnormalities, posterior cranial fossa widening or abnormalities of cerebellar vermis of fetus, whether fetal cleft lip accompanied by cleft palate or alveolar bone abnormalities, whether fetal auricle malformations associated with atresia of the external auditory canal or dysplasia of the middle and inner ears, extracardiac macrovascular malformations suspected by ultrasound examination, location and characterization of abdominal and pelvic masses, evaluation of intestinal malformations, genitourinary tract malformations and singleton twins complications, evaluation of curative effect and prognosis before and after treatment of fetal diseases, and evaluation before termination of pregnancy for severe diseases of fetus, etc.. Overall, fetal MRI examination can provide relevant information of fetus for prenatal diagnosis, eugenics and genetic counseling, and provide basis for fetal treatment plan formulation, delivery mode selection and doctor-patient communication. Although fetal MRI can make a standard and complete evaluation of fetal anatomy, it is still not the first choice for prenatal imaging diagnosis.