Assuming the regularity of the cycle and the possibility of sperm survival in the woman's body for up to 5-7 days, the risk of pregnancy with intercourse on the 1st day of the cycle is very small.

In order to minimize the risk of possible pregnancy, I encourage you to use an appropriate method of contraception, regardless of the day of the cycle. In order to choose the right method, I encourage you to consult a gynecologist. You can also take advantage of teleconsultation, e.g. via the Gdziepolek.pl portal:

https://www.gdziepolek.pl/telekonsultacja/z-ginekologiem

I encourage you to read our additional materials that may be useful:

https://www.gdziepolek.pl/artykuly/jak-prawidlowo-stosowac-antykoncepcje

https://www.gdziepolek.pl/kategorie/antykoncepcja