There is only moderate information concerning the use of calcium channel antagonists in pregnant women, most of it, however does deal with nifedipine. (Editor's Note: nifedipine is another name for Procardia.) While there is some animal data relating to congenital anomalies, they are minor, and to my knowledge not associated with the cardiovascular system, particularly the heart. I am not aware of any established teratogenicity in humans. These drugs are not used by most physicians who care for pregnant women. There is concern of precipitous drops in blood pressure when the short acting drugs are use when treating sudden rises in blood pressure. Concerning the long acting (slow release) drug, there is theoretical concern that because the drug works on the same calcium channels that magnesium does, the combined use of these drugs and Magnesium Sulfate that can arise if superimposed preeclampsia develops, may cuase magnesium toxicity. While there is little evidence for this, calcium channel blockers are not popular with those who manage hypertensive pregnant women.
I too know little about the cause or genetics of long QT syndrome and agree with the suggestion of discussing this with a pediatric cardiologist. She should also ask if the physician is aware of appropriate registries to mention the record the two cases that occurred in a mother ingesting nifedipine. Such registries (there is one for women who take antiepileptic drugs for example) make it possible to detect associations previously unknown. However, this too is an area I have not kept up with, (but pediatricians should know if they are Ã¢â‚¬Å“au courantÃ¢â‚¬Â).