Low risk HPV can sometimes cause a mild dysplasia (CIN1) but it is never the sole cause of a moderate (CIN2) or severe dysplasia (CIN3). There are studies where low risk HPV strains
as well. It is common to have strains of both low risk and high risk, did they perform an HPV test with your smear? As you likely know most mild cases of dysplasia will go away on their own and it is commong for pregnancy to create an environment for HPV to become active. The longer the virus is active the more likely it is for dysplasia to either develop or progress. Most often if it is pregnancy that brought about the active infection, with close monitoring and following the delivery the dysplasia will regress.