Purpose To study the structural changes in placental villi at altitude and in a preeclamptic disease state.
Methods Placentas from normal pregnancies were collected from three altitudes 0m, 1600m, and 3100m. Placentas from preeclamptic placenta at 3100m were also collected. Stereological analysis was performed on all samples to determine volume of villi, capillaries, stroma, interspace, thrombi, and cytotrophoblasts; surface density of villi and capillaries; capillary length density; capillary diameter; and morphometric diffusion capacity.
Results General Stereology: The samples were grouped by altitude (0m, 1600m, and 3100m); delivery method (vaginal and cesarean section); and normal vs. preeclampsia. Significant differences were not seen for vaginal vs. c-section delivery when compared for the same altitude with the same disease or normal state, thus have been grouped together. All 1600m normal placenta vs. all 3100m Preeclamptic (PE) placenta: PE placenta had lower volumes of interspace, surface area, and surface density of villi and capillaries. The PE placenta had higher volumes of cytotrophoblasts. Diffusing Capacity: 3100m normal vs. 3100m preeclamptic (PE): The PE placenta had lower birth weight and higher arithmetic means than normal placenta. 0m normal vs. 3100m PE: Birth weight was significantly decreased in the PE group compared to 0m normal. 1600m normal vs. 3100m PE: Arithmetic and harmonic means were increased in PE placenta compared to 1600m normal placenta. Surface area and MDC were decreased in PE placenta. Preeclamptic placenta had lower volumes of interspace, surface area, and surface density of villi and capillaries compared to normal placenta. A decrease in morphometric diffusion capacity occurred in placenta at high altitude and more so in the preeclamptic state.
Conclusion Placenta from altitude and preeclamptic conditions differ from normal, sea level, and low altitude samples. It appears that placenta in a preeclamptic condition fail to adapt to the hypobaric hypoxia of high altitude due to the decrease in diffusing capacity observed in these placenta. While preliminary, the data from the current study supports the theory that for some women the failure of the placenta to adapt structurally to hypobaric hypoxia can contribute to the development of preeclampsia.
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