ELEVATION OF SERUM CREATINE-PHOSPHOKINASE AND ITS MB ISOENZYME DURINGNORMAL LABOR AND EARLY PUERPERIUM

Background. Chest pain or discomfort are infrequent complaints among w omen during labor and early puerperium, but when present they raise th e suspicion of myocardial ischemia. The diagnosis of the latter is bas ed upon serum elevation of certain enzymes, such as aspartate amino tr ansferase, lactate dehydrogenase and creatine phosphokinase. Neverthel ess, the normal patterns of these enzymes in the serum during labor an d early puerperium have not been characterized well. Objective. To det ermine serum creatine phosphokinase, lactate dehydrogenase and asparta te amino transferase levels in late pregnancy, and throughout labor an d early puerperium. Methods. Fifty women having normal pregnancies fol lowed by uneventful vaginal deliveries were prospectively studied for serum lactate dehydrogenase, aspartate amino transferase and creatine phosphokinase including its MB isoenzyme before, during and after labo r. Cardiac status was evaluated in all women using serial electrocardi ographic and physical examinations. Results. All women were found to h ave low to normal antepartum serum enzymes levels. However, during lab or total creatine phosphokinase increased markedly, reaching a peak of 2-4 fold baseline levels 24 hours postpartum. It then declined gradua lly back to baseline. Nulliparous women reached substantially higher l evels than multiparous women. The MB or so-called cardiospecific isoen zyme was found to be an important contributor to creatine phosphokinas e surge in most women. Correlation was demonstrated between length of the active phase of labor and both total and MB creatine phosphokinase activity. There was no clinical or electrocardiographic evidence for cardiac muscle damage in any of the study patients. Serum lactate dehy drogenase and aspartate amino transferase were not altered during or a fter labor. Conclusions. Serum total creatine phosphokinase and its MB isoenzyme increase substantially during normal vaginal labor without evidence of myocardial ischemia. The uterus and placenta, two organs w hich were reported to embody substantial amounts of these enzymes, and which participate actively in the process of labor, are thought to re lease these enzymes to the circulation during labor. Knowing the norma l patterns of these enzymes in the serum during labor and puerperium m ay prevent erroneous diagnoses of myocardial ischemia or infarction. L ack of electrocardiographic abnormalities and low lactate dehydrogenas e and aspartate amino transferase levels may assist in excluding such diagnoses. (C) Acta Obstet Gynecol Scand 1996