Despite the seriousness of apparent life threatening events (ALTE), little is known about their epidemiology. The objective of this study was to derive a profile of 153 ALTE's recruited into the Collaborative Home Infant Evaluation (CHIME) and to compare it with published risk factors for sudden infant death syndrome (SIDS). 127 (83%) of the infants presented with classical features of apnea with either or both color and muscle tone changes. 12/127 (9%) had in addition choking, gagging, or vomiting. Twenty-six (17%) of the infants did not have apnea but had either change in color or muscle tone and most had both. Of these, 7 had minimal stimulation comprising those with the least serious event. Interventions were classified as vigorous stimulation (50%), mouth-to-mouth resuscitation (13%), chest compression (4%); 18% had more than one. Infants were followed for a minimum of 1 week to a maximum of 76 weeks with a median of 15 weeks. None died during follow-up. In contrast to SIDS mothers, the ALTE mothers were neither young nor old. The majority of ALTE were first born. One third of the mothers smoked, in contrast to more than two thirds of SIDS mothers. Most ALTE's occurred when the infants were 0-2 months old rather than 2-4 months as in SIDS. 34 (22%) of the infants were awake and 22 (14%) were in the supine sleeping position when the ALTE occurred. There was an excessive number of apnea and SIDS in family members of the ALTE group, not in siblings but in peripheral relatives. Preterm infants were over represented in both ALTE and SIDS. ALTE's were different from SIDS in age of mother, maternal smoking, birth order, timing of the episode, number of infants awake, and incidence in siblings. Cases were recruited based on parental selection influenced by their impression of the seriousness of the attack. In conclusion, the ALTE profile differs significantly from that of SIDS and calls into question their relationship.
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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