## Core Concept
The use of birth control pills (BCPs) can affect menstrual cycles due to their influence on the hypothalamic-pituitary-gonadal axis. When BCPs are discontinued, it may take some time for the body's natural hormonal balance to re-establish, leading to a delay in the resumption of normal menstrual cycles.

## Why the Correct Answer is Right
The correct answer, , indicates that about 90% of women can expect to resume normal menstrual cycles within 3 months after discontinuing birth control pills. This timeframe allows for the recovery of the hypothalamic-pituitary-ovarian axis, which is suppressed during BCP use. The resumption of menses is an indicator of ovulation and the return of fertility, although the return of fertility can vary among individuals.

## Why Each Wrong Option is Incorrect
**Option A:** - This option suggests a much lower percentage of women resuming normal menses within 3 months, which underestimates the actual proportion.

**Option B:** - This option suggests a slightly lower percentage than the correct answer but still underestimates the proportion of women who resume normal menses within 3 months.

**Option D:** - This option suggests a higher percentage than the correct answer, implying that nearly all women resume normal menses within 3 months, which overestimates the actual proportion.

## Clinical Pearl / High-Yield Fact
It's essential to note that while many women resume normal menstrual cycles within a few months after stopping BCPs, fertility may take longer to return in some cases. Women under 35 years old typically experience a quicker return of fertility compared to those over 35. A useful clinical pearl is that if menses do not resume within 6-12 months after stopping BCPs, further evaluation for causes of secondary amenorrhea should be considered.

**Correct Answer: C. **