Could she be prego?

It is biologically almost impossible for a woman to get pregnant one day after the end of her menstrual period. At that time, there is no mature egg inside her body waiting to be fertilized, and her date of ovulation is still many days in the future.

It is almost impossible because, when a woman is having a menstrual period, her uterus is disposing of the old, unused lining of the uterus that would have been used a nourish a fertilized, implanted egg if she had gotten pregnant earlier. It takes several days for this lining to rebuild itself. On the very REMOTE possibility that she could have had a mature egg in her body and it HAD been fertilized, it must still implant itself into the lining of the uterus before a pregnancy is established. When she is having having or just finishing a period, she HAS no lining. No lining = no implantation = no pregnancy.

This "precum" you are worried about. All that is, is the natural lubrication fluid that a male secretes from his penis during sexual arousal, in the same manner as a woman's vagina lubricates itself during sexual arousal. 99.7% of the time, it does NOT contain sperm cells. You could smear it all over her naked body, and she still would not get pregnant - not from "precum" alone. "Precum" itself is harmless. The gland in the male body that produces this lubrication (or "precum") is an entirely different gland than that which produces sperm cells.

Just about the ONLY way that a woman could get pregnant from "precum" would be if the man had very recently ejaculated, did not urinate afterward, and then put his penis inside her body. In that case, some stray sperm cells MIGHT remain in his urethra. He would be lubricating during this time, and that lubrication fluid (or "precum") MIGHT "wash out" those sperm cells into her body.

And PLEASE: Do not ask if she could be "prego"; not unless you are asking if she could be an Italian sauce. "Prego" is the brand name for a sauce that you buy in the grocery store, that is poured over pasta. Please say "pregnant", and not "prego".

any unprotected sex at any time of the month can result in a pregnancy