Establishing the time of intrauterine fetal death is important for determining the cause of its death. At autopsy, the time of death is determined by evaluating the severity of maceration processes of the external integument, internal organs and placenta. This study involves dissection of the body and organs, as well as the time spent on preparation of micropreparations.

Purpose. To study changes in organs and tissues of a deceased fetus depending on the time of its intrauterine death when using post-mortem MRI.

Material and methods. The work had been base on a comprehensive post-mortem radiation and autopsy studies of the bodies of 38 stillborn babies who were born at gestational periods of 22-40 weeks. Depending on the time of fetal death, all observations were divided into 8 groups. Postmortem MRI study was performed in standard T1 and T2 modes on the 3T Siemens Magnetom Verio device (Germany) before autopsy. On T1-and T2-weighted images (WI) in the sagittal projection, we determined the MR signal intensity of the liver, kidney, brain, femoral muscle, lung, skin in the hip area, anterior abdominal wall and fronto-parietal area of the head, as well as fluid in the pleural cavity and air near the anterior abdominal wall. Based on the obtained values, we calculated the MRI maceration index (MI) according to the formula: MI = (T2t / T1t) x (T1f / T2f) x (T1a / T2a), where T1t and T2t are the signal intensities of the studied tissue (t), T1f and T2f are the values of the signal intensity of the fluid (f) in the pleural cavity, T1a and T2a are the values of the intensity of the air signal (a) on T1- and T2-WI, respectively. The determination of the time of intrauterine death was carried out on the basis of the medical history of the pregnant woman, the history of childbirth, as well as the results of the pathological study.

Results. In observations with antenatal fetal death, the calculated MRI of the maceration index depended on the studied region (organ, tissue) of the fetus and the length of time that passed from the moment of death to childbirth. All MI of the internal organs and skin of the fronto-parietal region of the head had significant direct relationships with the statute of limitations of fetal death. Based on mathematical analysis, we derived the formula for determining the time of intrauterine death of the fetus, which expresses the result as the hours the fetus was found in utero after death (time of intrauterine death): t = 16.87 + 95.38x MIk ² - 75.32x MIk, where MIk - an indicator of maceration of kidney tissue.

Conclusion. The use of postmortem MRI allows making an objective quantitative assessment of the time of intrauterine death of the fetus, which contributes to the effective establishment of the links of the stillbirth. The advantages of post-mortem MRI over autopsy include the non-invasive nature of the study, the possibility of archiving and subsequent multiple analysis of tomograms, as well as the speed of MRI analysis compared with the time necessary for an autopsy and preparation of histological preparations for microscopic examination.