We thank Dr Field for his interest in our article and appreciate the opportunity to respond to the comments made in his letter.

Terbutaline is an agent used by obstetricians, including those in our center, as a tocolytic agent for preterm labor, although not in all cases. Unfortunately, during the design of our study, we did not consider the possibility raised by Dr Field of an effect of antenatal terbutaline exposure on positive screening for autism in ex-preterm infants; therefore, we do not have these data available for additional analyses. We acknowledge with interest the importance of other potential causes of autism summarized in Dr Field's commentary, and the issues raised should be considered in the design of future studies in this field.

You do not currently have access to this content.