Evaluation of Serum Anion gap in the three trimesters of Pregnancy in a Christian Religious Hospital in Benin City, Nigeria

This study is aimed at determining anion gap in the three trimesters of pregnancy. The study involved a total of 80 volunteers from the St. Philomena Catholic hospital, Benin City. The volunteers comprised 20 nonpregnant control, and 20 pregnant women in each of the three trimesters of pregnancy. Ethical approval was obtained from the Ethics and Collaboration committee of the hospital. Informed consents were also obtained from the participants. With strict aseptic method blood samples were drawn from the ante cubital vein into a lithium heparin bottle for electrolyte analysis using standard laboratory methods. Anion gap was subsequently calculated using the formula; ([Na⁺] + [K⁺]) − ([Cl^-] + [HCO3−]). Results were compared using the student’s t-test and p < 0.05 were considered statistically significant. The anion gap for the first trimester of pregnancy (11.01 ± 0.13 mmol/L) was significantly lower (p<0.05) than that of the control group (14.90 ± 0.43 mmol/L). The anion gaps for the second (14.78 ± 0.07 mmol/L) and third trimesters of pregnancy (14.90 ± 0.11 mmol/L) were essentially the same as that of the control subjects. The results may have been due to the variation in the gastrointestinal symptoms associated with the first trimester of pregnancy. However, the study indicates that pregnant women in their first trimester are more prone to abnormal serum anion gap which is a function of blood electrolyte concentration. This finding should be reflected by antenatal care givers and antenatal care policy makers to forestall untoward effect of abnormal serum anion gap.