STUDY OF SEASONAL VARIATIONS IN 9 CATIONS OF NORMAL TERM PLACENTAS

Sodium, potassium, calcium, magnesium, zinc, lead, copper, and iron levels were determined in human term placentas collected daily through one calendar year. All measurements were performed by atomic absorption spectrophotometry and expressed as moles per gram of dry tissue weight. The resultant data indicate a seasonal variation in the mean monthly placental levels of sodium, potassium, magnesium, and lead. Differences were not observed when the data were grouped according to race, maternal age, or gravidity. © 1968.