Edit the text to be more cohesive:
Diazepam and clonazepam have been found to have long-lasting, but not permanent, immunotoxic effects in the fetus of pregnant rats. Single very high doses of diazepam have been found to cause lifelong immunosuppression in neonatal rats.
Diazepam and clonazepam have been found to have long-lasting, but not permanent, immunotoxic effects in the fetus of pregnant rats. However, single very high doses of diazepam have been found to cause lifelong immunosuppression in neonatal rats.