What does the start of menses indicate?

• A. The next cycle has begun and is counted as day 1 of the cycle
• B. Fertility peak
• C. Ovulation has just occurred
• D. Pregnancy has started

Answer: (A)

The start of menses marks the beginning of a new menstrual cycle; the first day of bleeding is day 1. This happens after the previous cycle’s ovulation and if fertilization/implantation doesn’t occur, hormone levels (estrogen and progesterone) fall and the endometrium sheds. That shedding produces the bleeding that starts the cycle anew. Fertility is highest around ovulation in the middle of the cycle, not at the start of menses. Pregnancy would usually stop menses because hormonal support from pregnancy halts the shedding. So the start of menses best indicates that a new cycle has begun and day 1 has started.