Concerta was rated a pregnancy Category C medication because it was shown to cause birth defects in rabbits. In these studies, pregnant rabbits were given very high doses of Concerta.

Category C meaning.
Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.

This is taken directly from
http://adhd.emedtv.com/concerta/concerta-and-pregnancy.html
References :
Directly from
http://adhd.emedtv.com/concerta/concerta-and-pregnancy.html

Concerta and Pregnancy Category C
The U.S. Food and Drug Administration (FDA) uses a pregnancy category system to classify the possible risks to a fetus when a specific medicine is taken during pregnancy. Pregnancy Category C is given to medicines that have not been studied in pregnant humans, but do appear to cause harm to the fetus in animal studies. Also, medicines that have not been studied in any pregnant women or animals are automatically given a pregnancy Category C rating.

Concerta was rated a pregnancy Category C medication because it was shown to cause birth defects in rabbits. In these studies, pregnant rabbits were given very high doses of Concerta.

However, it is important to note that animals do not always respond to medicines in the same way that humans do. Therefore, a pregnancy Category C medicine may be given to a pregnant woman if the healthcare provider believes that the benefits to the pregnant woman outweigh any possible risks to the unborn child.

Recommendations for Using Concerta During Pregnancy
If you are pregnant or thinking about becoming pregnant, let your healthcare provider know. Your healthcare provider will consider both the benefits and the risks of taking Concerta during pregnancy before making a recommendation for your particular situation
References :

I would not take answer on here about any drug and my pregnancy

If you want to know before the appointment, call the doctor office, they will get back to you
References :