Topical Retinoids During Pregnancy

Although tretinoin (the active ingredient in Retin-a) is a pregnancy category C medication and therefore, not recommended during pregnancy, any harm you may have caused to the fetus at this point is extremely unlikely. I would, however, recommend you discontinue use of Retin-a at this time since a small risk is, nonetheless, still a risk.

Tretinoin (Retin-A and Renova) which are used to treat acne and other skin issues belong to the retinoid group - all of whose members are related to Vit. A. Other members of the group are isotretinoin (Accutane), adapalene (Differin), and etretinate.
All drugs are classified based on their potential risk to the fetus from Class A (no restrictions) to Class B, Class C, Class D, and and Class X (absolutely prohibited). Retin-A is a Class C drug for pregnancy. (meaning that the potential risks of taking it during pregnancy should be outweighed by the benefits). Contrast it with Accutane (isotretinoin ) which is extremely harmful in pregnancy and is a Class X drug.
In your case, I WOULD stop the tretinoin and see your OB for his/her opinion. But I would not worry too much, according to the source below "...studies have not found that babies whose mothers used tretinoin during pregnancy are any more likely to have birth defects than babies whose mothers did not use tretinoin."
Good Luck
Dr. P. Aldea