Differin is not approved for use during pregnancy, but others are OK
Differin is not approved for use during pregnancy, but there are other acne medications that are safe to use. I found an article on skintour.com under 'resources' called 'pregnancy and safe skin care' which you should check out.
Differin is pregnancy category C which means it was not tested in pregnancy and it is not know if it is safe. We do know that Differin is safe during breastfeeding so there must be very little if any product that gets absorbed internally and most likely had no effect.
However, since we do not know, Differin should not be used during pregnancy.