Physiological Arterial Remodeling: When is It Abnormal?

Objectives: Pinpoint the exact moment during the second quarter of pregnancy when spiral arteries remodeling can be considered abnormal. Arterial transformation begins at a very early gestational stage; however, on the basis of standard histopathological samples, it is still not possible to determine it. Uterine arteries must undergo the remodeling process in order to be transformed into flexible tubes able to supply the growing fetus with nutrients and oxygen. If this process does not take place, spontaneous abortions, stunted intrauterine growth and pregnancy-related hypertensive disorders, especially preeclampsia, may result.
Methods: 100 samples from consecutive abortions taken at 12 to 23 gestational weeks were examined from the Vall d´Hebron Hospital tissue bank. Blinded pathologists assessed clinical data of slides and determined the remodeling stages, according to previously published guidelines
Results: Pathologists´ assessments revealed that arterial remodeling is not synchronic in all vessels; a single sample can include various remodeling stages; neither is remodeling homogenous in a single vessel: change may be occurring in one part of the vessel, but not in another. We have not published our observations on these assessments. In the examined age group, Smith Stage 4 predominated (2009); around week 14 substantial muscle and endothelium loss takes place. After week 17, endovascular or fibrin trophoblast is not expected to occur.
Conclusion: Although there is a lack of consensus on what causes preeclampsia, it is clear that abnormal remodeling in maternal decidua vessels is involved. A better understanding of this disorder requires greater knowledge of both the physiological and pathological aspects of the remodeling process. Our conclusion is that muscle and endothelial tissues disappear in the basal decidua arteries from weeks 14 to 17, after which time reendothelialization prevails.