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Letter to the Editor
Editor, – In addition to the tests mentioned in the article 'Abnormal laboratory results: Biochemical tests in pregnancy' (Aust Prescr 2005;28:98-101), there are several other tests where the changes in the normal ranges during pregnancy are of clinical importance.
- Serum bicarbonate falls by approximately 4 mmol/L to compensate for the respiratory alkalosis which results from elevated progesterone concentrations stimulating respiratory drive.1
- Serum vitamin B12falls in 25% of pregnant women such that a value of greater than 100 pmol/L should be regarded as normal for pregnancy. In the absence of folate deficiency serum homocysteine is of value in establishing true B12deficiency in pregnancy.23
- Erythrocyte sedimentation rate rises significantly (often up to 100 mm/hour).4
- White cell count rises due to neutrophil leucocytosis.5
- D-dimer becomes elevated in second and third trimesters.6
- Free protein S concentrations fall significantly.7
- Creatine kinase (MB subfraction) rises after vaginal delivery.8
- Serum troponin may be elevated in pre-eclampsia making diagnosis of myocardial ischaemia problematic if mothers develop pulmonary oedema.9
- Plasma renin activity and serum aldosterone rise masking detection of primary aldosteronism as a cause of pre-gestational hypertension in pregnancy.10
Senior staff specialist, Endocrinology and Obstetric Medicine
Mater Adult Hospital
- McAuliffe F, Kametas N, Krampl E, Ernsting J, Nicolaides K. Blood gases in pregnancy at sea level and at high altitude. BJOG 2001;108:980-5.
- Metz J, McGrath K, Bennett M, Hyland K, Bottiglieri T. Biochemical indices of vitamin B12 nutrition in pregnant patients with subnormal serum vitamin B12 levels. Am J Hematol 1995;48:251-5.
- Pardo J, Gindes L, Orvieto R. Cobalamin (vitamin B12) metabolism during pregnancy. Int J Gynaecol Obstet 2004;84:77-8.
- Salawu L, Durosinmi MA. Erythrocyte rate and plasma viscosity in health and disease. Niger J Med 2001;10:11-3.
- Karim SA, Khurshid M, Rizvi JH, Jafarey SN, Rizwana I. Platelets and leucocyte counts in pregnancy. J Pak Med Assoc 1992;42:86-7.
- Kline JA, Williams GW, Hernandez-Nino J. D-dimer concentrations in normal pregnancy: new diagnostic thresholds are needed. Clin Chem 2005;51:825-9.
- Wickstrom K, Edelstam G, Lowbeer CH, Hansson LO, Siegbahn A. Reference intervals for plasma levels of fibronectin, von Willebrand factor, free protein S and antithrombin during third-trimester pregnancy. Scand J Clin Lab Invest 2004;64:31-40.
- Leiserowitz GS, Evans AT, Samuels SJ, Omand K, Kost GJ. Creatine kinase and its MB isoenzyme in the third trimester and the peripartum period. J Reprod Med 1992;37:910-6.
- Fleming SM, O'Gorman T, Finn J, Grimes H, Daly K, Morrison JJ. Cardiac troponin I in pre-eclampsia and gestational hypertension. BJOG 2000;107:1417-20.
- 10. Bentley-Lewis R, Graves SW, Seely EW. The renin-aldosterone response to stimulation and suppression during normal pregnancy. Hypertens Pregnancy 2005;24:1-16.
- Bentley-Lewis R, Graves SW, Seely EW. The renin-aldosterone response to stimulation and suppression during normal pregnancy. Hypertens Pregnancy 2005;24:1-16.
- Koebnick C, Heins UA, Dagnelie PC, Wickramasinghe SN, Ratnayaka ID, Hothorn T, et al. Longitudinal concentrations of vitamin B(12) and vitamin B(12)-binding proteins during uncomplicated pregnancy. Clin Chem 2002;48:928-33.
- van den Broe NR, Letsky EA. Pregnancy and the erythrocyte sedimentation rate. BJOG 2001;108:1164-7.
- Hiss RG. Evaluation of the anaemic patient. In: Laros Jr RK, editor. Blood disorders in pregnancy. Philadelphia: Lea & Febiger; 1986. p. 9.