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Table 1 Semi-quantitative correlation of placental types with Thy-1 expression, morphology of villous sinusoids and expression of cyclin E low molecular weight variants (cE LMW) for details and quantitative evaluation see Ref. [30], and ERα expression (this study) in normal (NP) and abnormal (AP) basic placental categories and placental types (PT1–PT4).

From: Expression and localization of estrogen receptor-alpha protein in normal and abnormal term placentae and stimulation of trophoblast differentiation by estradiol

Basic categories Placental types Placental size Dominant villi Villous Thy-1 Dilatation of sinusoids cE LMW variants ERα protein expression
NP, ERα+ PT1a Normal mature high low all low strong
  PT2b Normal mature moderate moderate all higher vs. PT1 strong
AP, ERα- PT3c Normal aged low excessive some higher traces
  PT4Ad Hypertrophy young traces low some higher traces
  PT4Be Atrophy immature traces low some higher traces
  1. aPT1, normal placental type, with occasional development of new mature villi or expansion of existing villi to fulfill the demands of the progressively growing fetus. Rarely, if there is no requirement for villous replacement or expansion, the ERα might not be expressed. bPT2, marginal irregularity, which can be interpreted as a compensation of imminent placental aging by enhanced development of new villi associated with expansion of existing mature villi and moderate dilatation of villous sinusoids. cPT3, placental senescence associated with the extreme dilatation of villous blood sinusoids and no compensatory villous development or expansion. dPT4A, placental hypertrophy – terminal villi persist in a young/immature state with compensatory development of additional young terminal villi (maternal diabetes mellitus associated with fetal macrosomia). ePT4B, placental atrophy – terminal villi persist in a young/immature state without compensatory development of additional young terminal villi (intrauterine growth retardation and poor Apgars).