Biochemical changes in prolonged labour in the tropics.

Serum electrolytes, creatinine, urea and urine osmolality were estimated in 25 healthy pregnant women at term, 25 women in early normal labour, and 25 healthy parturients in prolonged labour. A statistically significant fall in serum potassium was found in early labour with a further significant fall in prolonged labour. Bicarbonate changes followed the same pattern of a progressive fall. Sodium fell slowly, reaching significant levels only in prolonged labour and chloride fell even more slowly. There was a conspicuous or significant rise in serum urea with a smaller, not significant rise in creatinine. The rapid insensible loss of water in tropical areas was reflected in the rise in serum urea while homeostatic mechanisms maintained a slower fall in sodium and chloride by renal conservation.