Histopathological findings of pregnancy-induced hypertension: histopathology of early-onset type reflects two-stage disorder theory.

The placental tissues of pregnancy-induced hypertension (PIH) patients exhibit multiple infarctions, acute atherosis, distal villous hypoplasia, and increased syncytial knots. However, these findings are not observed in all cases of PIH; thus, the significance of these changes in PIH is still unclear. We studied the frequency of histopathological changes of placental tissue in the subgroups of PIH, such as mild and severe PIH and early-onset (< 34 weeks) and late-onset (≥ 34 weeks) PIH. One hundred seven cases of PIH diagnosed at the Shinshu University Hospital, Matsumoto, Japan, between 2008 and 2014 were collected. PIH includes preeclampsia and gestational hypertension. The pathologic changes evaluated in the placenta were multiple infarctions, acute atherosis, distal villous hypoplasia, and increased syncytial knots. Placental tissues of patients with early-onset PIH demonstrated acute atherosis resulting from the incomplete remodeling of the spiral arteries and distal villous hypoplasia and increased syncytial knots reflecting placental hypoxia/ischemia much more frequently than those with late-onset PIH (all p < 0.001). The frequencies of multiple infarctions did not show a statistical difference between early-onset PIH and late-onset PIH. Moreover, there were no significant differences in the frequencies of histopathological features of placental tissue between mild PIH and severe PIH. Early-onset PIH exhibited histopathological changes of placental tissue consistent with the two-stage disorder theory more frequently than late-onset PIH. These findings support the idea that early-onset PIH and late-onset PIH are distinct entities or different extremes of the PIH spectrum.