Is there any specific reason why a pregnant woman with hypertension who has been taking bystolic for over a year should not continue that med? (labetalol not well tolerated) anything definitive found in literature that supports a contraindication?

It can be used if necessary and there is no absolute contraindication.

There have been and there still are questions concerning the use of beta blockers during pregnancy with regard to adverse effects on the fetus. Any decision regarding the use of beta blockers need to be made after full discussion with the patient, the obstetrician and and the internist/cardiologist. Many experts have commented upon the risks of beta blockers and ACE inhibitors during pregnancy.