We studied drug-induced cardiotoxic effects in 22 pregnant women having tocolysis with intravenous fenoterol and verapamil. Because CK-MB is released from the uterus and placenta, we used the determination of cardiac troponin T (cTnT) as it is one of the most sensitive and specific indicators of myocardial necrosis. Cardiac troponin T levels were within physiological range (0.08 +/- 0.01 microgram/l) in all healthy pregnant women tested between 32 and 36 weeks of gestation (control group). In the pregnant women having tocolysis cTnT levels started to increase slightly during the first day of treatment (0.10 +/- 0.03 microgram/l) and were significantly higher (p < 0.05) during the third day (0.35 +/- 0.14 microgram/l) of tocolytic therapy. The cTnT levels in cord blood (0.13 +/- 0.03 microgram/l) did not correspond with maternal cTnT concentrations.