Reference intervals for anion gap and strong ion difference in pregnancy: a pilot study.

Area of Science:

• Physiology
• Obstetrics
• Biochemistry

Background:

• Normal pregnancy is characterized by significant physiological alterations in acid-base status and electrolyte levels.
• Understanding these changes is essential for accurate interpretation of laboratory values during pregnancy.

Purpose of the Study:

• To investigate the impact of physiological changes during normal pregnancy on the anion gap.
• To determine how pregnancy affects the strong ion difference (SID).

Main Methods:

• A cross-sectional study design was employed.
• Participants included normal pregnant women across three trimesters and a postpartum group.
• Anion gap and SID were measured in all participants.

Main Results:

• The anion gap was significantly lower in pregnant women (8.5 +/- 2.9 mEq/L) compared to postpartum values (10.7 +/- 2.5 mEq/L).
• The strong ion difference (SID) was also reduced during pregnancy (38.3 +/- 2.9 mEq/L) versus postpartum (43.5 +/- 2.3 mEq/L).
• These reductions in anion gap and SID reflect combined influences of changes in albumin, SID, and PCO(2).

Conclusions:

• Both the anion gap and strong ion difference (SID) decrease during normal pregnancy.
• These findings necessitate consideration when evaluating and managing acid-base disturbances in pregnant individuals.