Which electrolyte change is observed by mid-pregnancy?

Which electrolyte change is observed by mid-pregnancy?

• A. Calcium decreases about 10%
• B. Chloride increases by 5 mEq/L
• C. Potassium increases 0.2 to 0.3 mEq/L
• D. Sodium increases 2 to 4 mEq/L

Answer: (A)

During pregnancy, plasma volume expands significantly, which dilutes circulating solutes and minerals. By mid-pregnancy this dilution commonly shows up as a drop in total calcium levels—about 10% lower than nonpregnant values. This reflects the balance of increased fetal calcium demands and maternal adaptive changes; ionized calcium tends to stay normal even as total calcium falls. The other electrolyte shifts described are not typical mid-pregnancy changes. Sodium usually remains within normal limits or changes only slightly due to volume expansion, not a clear increase of 2 to 4 mEq/L. Chloride and potassium do not show a consistent, pronounced rise during this stage of pregnancy. So the observed change by mid-pregnancy is a notable decrease in calcium around 10%.

During pregnancy, plasma volume expands significantly, which dilutes circulating solutes and minerals. By mid-pregnancy this dilution commonly shows up as a drop in total calcium levels—about 10% lower than nonpregnant values. This reflects the balance of increased fetal calcium demands and maternal adaptive changes; ionized calcium tends to stay normal even as total calcium falls.

The other electrolyte shifts described are not typical mid-pregnancy changes. Sodium usually remains within normal limits or changes only slightly due to volume expansion, not a clear increase of 2 to 4 mEq/L. Chloride and potassium do not show a consistent, pronounced rise during this stage of pregnancy.

So the observed change by mid-pregnancy is a notable decrease in calcium around 10%.