Which phase is characterized by endometrial thickening in preparation for potential implantation?

• A. Secretory Phase
• B. Proliferative Phase
• C. Ovulation Phase
• D. Luteal Phase

Answer: (B)

Endometrial thickening in preparation for implantation is driven by estrogen stimulating the lining to grow and rebuild after menstruation. This rapid growth and thickening happen during the proliferative phase, as the lining responds to the rising estrogen from the maturing ovarian follicle. The goal of this phase is to create a thick, receptive lining in case fertilization occurs.

After ovulation, progesterone from the corpus luteum shifts the uterus into the secretory phase, where glands become more secretory and the tissue becomes ready to sustain an implanted embryo if fertilization happens. If no pregnancy occurs, falling hormones lead to shedding of the lining in the next menstrual phase. Ovulation itself is the release of the egg, not the thickening process of the endometrium.