• β-adrenoceptor;
  • cardiac development;
  • preterm labor;
  • terbutaline;
  • tocolysis


BACKGROUND: β2-Adrenoceptor (βAR) agonists, such as terbutaline, are widely used to arrest preterm labor. They also cross the placenta where they stimulate receptors in fetal tissues, which in turn use βAR input for trophic control of cell replication and differentiation.

METHODS: As rats are altricial, we administered terbutaline in two different postnatal exposure periods (10 mg/kg given daily on Days 2–5 or 11–14).

RESULTS: Hearts were examined twenty-four hours after the last dose and on postnatal day 30 for cardiac damage. Neither treatment paradigm caused an increase in cardiac abnormalities compared to controls but quantitative analysis of the number of nuclei indicated reductions in females.

CONCLUSIONS: These findings do not support earlier case reports of outright myocardial necrosis after terbutaline tocolysis in human infants. Nevertheless, the significant statistical association between terbutaline and cardiac anomalies in epidemiological studies suggest that terbutaline may sensitize the developing heart to other insults that affect development. Birth Defects Res B 68:449–455, 2003. © 2003 Wiley-Liss, Inc.