Regarding the commentary by Witter et al, the authors go to great lengths to emphasize the possible risks and to dismiss the possible benefits of maintenance beta 2 agonist therapy in the management of preterm labor. Indeed, the data supporting the use of maintenance tocolysis with beta 2 adrenergic agents are limited to retrospective studies, but the 2 negative prospective trials quoted by the authors are limited by their small sample size and were underpowered to avoid a type II error. Therefore, the benefit of maintenance terbutaline therapy must be considered unknown. Furthermore, despite the references cited by the authors, in our opinion the risks of this therapy are also unknown. The studies cited linking maintenance beta 2 agonist therapy to autism are significantly limited by bias. A case-control study demonstrating that children with autism were more likely to have been exposed to tocolytics in utero obviously has confounders such as prematurity, inflammation, and infection. Are the authors willing to concur with the statement made in one of their references that “mechanisms causing premature labor do not seem to specifically increase the risk of autism and are unlikely factors in the increased relative risk noted in this study” ? We believe this statement is false and that the link between beta 2 agonists and autism is at best associative and not necessarily causal.

In our opinion, the only way to determine the actual effectiveness and risk of maintenance beta 2 agonist therapy is with a properly powered prospective randomized trial, something that has yet to be done.