What are the chances of a precum conception?

Patient: What are the chances i got my girlfriend pregnant from precum conception? I ejaculated twelve hours before intercourse and can’t remember if I urinated. Her period just ended the day before, so I assume ovulation hasn’t occured yet. In addition, i only entered the uterus half way from the cervix. Her menstruation cycle is irregular as well and can be either two to three weeks or one in two months.

Symptoms: None