**Core Concept**
The return of menstrual cycles in lactating women is influenced by the interplay between prolactin, estrogen, and progesterone levels. Prolactin, which is essential for milk production, suppresses the secretion of gonadotropin-releasing hormone (GnRH), leading to reduced follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels. As a result, ovulation and menstruation are delayed.

**Why the Correct Answer is Right**
The resumption of menstrual cycles typically occurs when the woman stops breastfeeding and her prolactin levels decrease. This decrease allows for the restoration of the hypothalamic-pituitary-gonadal axis, enabling the release of FSH and LH, which stimulate follicle growth and ovulation. The first menstrual flow, also known as the first menstrual period postpartum (FMP), usually begins 6-8 weeks after delivery in non-breastfeeding women.

**Why Each Wrong Option is Incorrect**
**Option A:** 2 weeks - This is too early for the first menstrual flow to occur, even in non-lactating women.
**Option B:** 12 weeks - While some women may experience a delay, 12 weeks is generally longer than the typical time frame for the resumption of menstrual cycles.
**Option C:** 16 weeks - This is excessively long and not a common time frame for the return of menstrual cycles.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the return of menstrual cycles in lactating women can be influenced by factors such as the frequency and duration of breastfeeding, the mother's overall health, and the presence of any underlying medical conditions.

**Correct Answer:** C. 8 weeks.