Placental bed disorders in preterm labor, preterm PROM, spontaneous abortion and abruptio placentae.

Failure of physiologic transformation of the spiral arteries has been studied using placental bed biopsies in several obstetrical syndromes. Contrary to what was originally believed, this lesion is not restricted to preeclampsia and/or intrauterine growth restriction. A review of published evidence indicates that failure of physiologic transformation can be observed in women with spontaneous second trimester abortions, preterm labor with intact membranes, preterm prelabor rupture of membranes and abruptio placentae. Therefore, disorders of deep placentation are present in a wide range of complications of pregnancy, emphasizing the importance of understanding the physiology and pathology of transformation of the spiral arteries. We propose that changes in the population and function of immunocytes at the maternal-fetal interface can be part of the mechanism of disease of obstetrical disorders, and this requires further investigation.