Serum sodium and potassium values in pregnant urban Nigerian and Caucasian women.

Serum sodium and potassium values were determined in the same laboratory for 250 pregnant urban Africans, 31 non-pregnant urban Africans and 155 pregnant Caucasians. The non-pregnant urban African women had significantly higher average serum sodium concentration than both pregnant groups. There was a progressive decline in serum sodium in both groups of pregnant women starting from the end of the first trimester to term. The decline in sodium concentration did not approach the level of hyponatraemia as previously reported. The fall in serum sodium concentration during pregnancy is probably a general phenomenon for pregnant women. The serum potassium concentration of the pregnant African women was not significantly higher than that of their non-pregnant counterparts. However, in pregnant Caucasians it was significantly higher than in pregnant and non-pregnant Africans. Serum potassium concentrations showed no significant variation during pregnancy.