Maternal cardiac troponin I levels during normal labor and delivery

Diagnosis of myocardial infarction in pregnant women on the basis of changes in biochemical markers is complicated by the release of some of these markers from noncardiac tissue sources. We compared troponin I levels with those of other markers in normal pregnant women.

In 51 healthy women at term in labor, cardiac troponin I, myoglobin, creatine kinase, and creatine kinase MB levels were determined at admission, during the second stage of labor, and within 30 minutes, 12 hours, and 24 hours after delivery.

Mean admission levels for all markers were below the upper limit of normal. Mean concentrations of myoglobin, creatine kinase, and creatine kinase MB mass were increased nearly twofold within 30 minutes after delivery. The highest level of troponin I (0.134 ng/mL) at all time points was below the cutoff value (0.15 ng/mL) for discriminating myocardial infarction.

Because only troponin I levels remained undetectable during and after delivery, it is potentially the most useful biochemical marker for monitoring pregnant women for myocardial injury.