Engaging in sexual intercourse on the second day of one's menstrual cycle does carry a theoretical risk of pregnancy, albeit significantly lower compared to other days of the menstrual cycle. While the likelihood of conception is diminished during this phase due to the low probability of ovulation, it is not entirely impossible. Sperm can survive within the female reproductive tract for up to five days, thus if ovulation occurs shortly after menstruation ceases, there exists a window of opportunity for fertilization to transpire.

However, it is crucial to understand that each woman's menstrual cycle is unique, and ovulation timing can vary. Factors such as cycle length, hormonal fluctuations, and individual reproductive health can influence the precise timing of ovulation. Consequently, relying solely on the calendar method for contraception during the early days of the menstrual cycle may not be sufficiently reliable for preventing pregnancy.

For individuals seeking to avoid unintended pregnancy, it is advisable to employ more effective contraceptive methods, such as barrier methods (e.g., condoms), hormonal contraceptives (e.g., birth control pills, patches, or injections), or intrauterine devices (IUDs). These methods offer higher efficacy rates and provide greater protection against pregnancy throughout the menstrual cycle.

In summary, while the probability of conception is lower during the initial days of menstruation, the risk still exists, albeit minimally. Employing reliable contraception is paramount for individuals wishing to prevent unwanted pregnancy, as relying solely on timing may not suffice to ensure contraceptive efficacy.