The follicular phase is the first half of the menstrual cycle, beginning on Day 1 of menstruation and ending at ovulation.
- It is named after the follicles in the ovaries, which begin to develop and mature in preparation for the release of an egg.
📆 Timeline and Duration:
- Begins on Day 1 of the cycle (the first day of menstrual bleeding)
- Ends when ovulation occurs (typically around Day 14 in a 28-day cycle)
- Can vary in length, especially in cycles that are irregular — unlike the luteal phase, which is usually more consistent
🧬 What happens during the follicular phase?
| Biological Event | Description |
|---|
| 🩸 Menstruation starts | Uterine lining sheds if no pregnancy occurred in the prior cycle |
| 🧪 FSH rises | Follicle-stimulating hormone (FSH) tells the ovaries to begin maturing several follicles |
| 🌟 Dominant follicle emerges | One follicle becomes dominant (called the Graafian follicle) and prepares to release an egg |
| 💧 Estrogen increases | The dominant follicle produces estrogen, which rebuilds the uterine lining (endometrium) and prepares for possible implantation |
| 🔼 LH surge | Rising estrogen triggers a spike in luteinizing hormone (LH), which causes ovulation |
🔬 Hormonal Profile:
- FSH initiates follicle development
- Estrogen dominates this phase — supports uterine lining growth and fertile cervical mucus
🧠 Why the follicular phase matters:
- Prepares the body for fertilization and implantation
- Controls cycle length variability (if cycles are irregular, it’s usually the follicular phase that’s longer or shorter)
- Key for identifying fertile days in fertility awareness
✅ Summary Table
| Term | Definition |
|---|
| Follicular Phase | First half of the cycle, from menstruation to ovulation |
| Starts | On the first day of the period (Day 1) |
| Ends | At ovulation |
| Dominant Hormone | Estrogen |
| Main Events | Follicle growth, uterine lining rebuilds, fertile window opens |
