It has been shown that MRI offers the possibility of more detailed assessment of fetal pathology than sonography. It is used not only to diagnose but also to follow up some prenatal diseases. It is a basis of in utero treatment and the tool of monitoring its efficacy The purpose of the study was to present the authors' experience with prenatal MRI as a method of follow-up of fetal pathology and of monitoring invasive fetal therapyThe study group consisted of 31 fetuses that underwent two MRI examinations. The first exams were performed at the gestational age of 19-28 weeks (mean: 23.6 weeks), the follow-up between week 20 and 37 (mean: 30.5). The MRI examinations were performed using 1.5 T scanners. SSFSE/T2-weighted images, TSE/ or GRE/T1-weighted images, DWI, FIESTA, EPIGRE were performed.In 5 cases MRI allowed to exclude a suspected pathology: brain anomaly in a healthy fetus, septo-optic dysplasia in a healthy fetus, right-sided CDH in case of a left-sided pathology pentalogy of Cantrell, lack of bladder in a fetus with a small, thick-walled bladder In 4 cases an additional pathology was detected on MRI: CCAM/ pulmonary sequestration with self-regression, cerebellar hypoplasia, rhombencephalosynapsis, tethered cord with syringohydromyelia. In 4 cases MRI was used just to follow-up and showed evolution of the disease in 2 cases: regression of intracerebral hemorrhage, progression of kidney disease. Finally, in 18 cases MRI was performed before and after an open fetal surgery of myelomeningocele showing good outcome in 10 cases and a wide spectrum of complications in 8 neonates: from edema of the transplant only in 4 to recurrent MC in 1.Maternal uterus constitutes a natural "incubator" for the fetus--it is easier and safer to perform diagnostic procedure in utero than in a seriously ill newborn. MRI is a method of choice in the diagnosis and of follow-up in cases of open fetal surgery.