Placental pathology varies in hypertensive conditions of pregnancy.

This study was a comprehensive analysis of placental phenotypes in hypertensive conditions of pregnancy, including recently described placental hypoxic lesions and lesions of shallow placentation. To this end, consecutive placentas from > 21 weeks pregnancies that were signed out by the author at 4 tertiary care centers on 3 continents were included. Twenty-four clinical and 50 placental phenotypes were studied in 6 groups and statistically compared: 91 cases of gestational hypertension, 187 cases of mild preeclampsia, 211 cases of severe preeclampsia, 84 cases of HELLP or eclampsia, 127 cases of chronic hypertension, and 55 cases of preeclampsia superimposed on chronic hypertension. Twenty percent of the placental and clinical phenotypes were statistically significantly different between the groups. Gestational hypertension and chronic hypertension distinguished themselves by having the highest perinatal mortality, lowest cesarean section rates, highest acute chorioamnionitis, and highest fetal vascular ectasia but conspicuously fewer differences in hypoxic and thrombotic lesions. The preeclamptic groups showed the highest rates of decidual arteriolopathy (both hypertrophic and atherosis), uterine pattern of chronic placental injury, villous infarctions, and clusters of maternal floor multinucleate trophoblasts. Based on placental pathology, severe preeclampsia may be more of a placental disease and mild preeclampsia more of a maternal disease; however, the significant overlap among the groups does not make the difference absolute, and the occurrence of decidual arteriolopathy in gestational hypertension and chronic hypertension may indicate that the conditions could be regarded as "occult preeclampsia."