In a typical 28-day cycle, the most fertile days occur during which days?

• A. 21-28
• B. 1-6
• C. 9-16
• D. 6-9

Answer: (C)

The key idea is the fertile window around ovulation. In a typical 28-day cycle, ovulation happens about mid-cycle, around day 14, triggered by the LH surge. The egg is viable for about 12–24 hours after release, and sperm can live in the reproductive tract for up to about five days. Put together, conception is most likely when intercourse occurs in the days leading up to ovulation and on the day of ovulation. This makes roughly days 9 through 16 the best estimate for the fertile window, with day 14 as the peak. The other time frames fall outside this window—earlier days are before ovulation, and later days are after ovulation, when fertility is lower.