Had sex with my pregnant wife while on treatment with fluorouracil

Patient: I am an adult male with a younger wife who is six months pregnant. One week ago I was diagnosed with having a pre-cancerous lesion on my right shin. The diagnosing dermatologist prescribed Fluorouracil 5% topical cream for 3 weeks to kill the lesion. When I read the warnings regarding the drug I took the pregnancy warnings to be applicable to the first person so being a male I essentially ignored them. I have had sex with my wife just once. It took place last night. My question is whether a significant amount of the drug to endanger the pregnancy would be built up in my system after two small applications per day for 7 days? I have since researched this but can only find small population studies that report no adverse exposure results for pregnant women. I will not have any further sex with my wife until well after she delivers but am ridden with guilt that I did not research this before I exposed her to my semen.

Doctor: With the use of topical fluorouracil 5%, the amount that gets absorbed into your system is very low and insignificant. I t may not affect your wife and the unborn baby. Serious harmful effects on the fetus may occur with oral dose, IV or topical application on the mucous membrane or vagina in pregnant women. Use of this medication in males usually cause sperm abnormalities leading to infertility or fetal anomaly. However use of proper contraception is recommended up to 6 months after the completion of the treatment.