What is Menstrual Cycle?
💡 The menstrual cycle is the monthly hormonal cycle (21–35 days) governing female reproduction. Phases: menstruation → follicular phase (FSH-driven follicle growth) → ovulation (LH surge, Day ~14) → luteal phase (progesterone dominance). Irregular cycles (>35 days) indicate ovulatory dysfunction.
The menstrual cycle is the monthly hormonal cycle that prepares the female body for pregnancy. It encompasses follicle development, ovulation, endometrial preparation, and — in the absence of conception — menstruation. A normal cycle is 21–35 days; irregular cycles are a primary sign of ovulatory dysfunction.
🇮🇳 India Context: Menstrual Cycle is widely assessed and treated across major Indian fertility centres including Chennai, Mumbai, Bangalore, Delhi, and Hyderabad.
What are the key characteristics of Menstrual Cycle?
- Normal cycle length: 21–35 days; median 28 days — counted from Day 1 of full bleeding to Day 1 of the next
- Four phases: menstruation (Days 1–5), follicular phase (Days 1–13), ovulation (Day ~14), luteal phase (Days 15–28)
- Governed by the hypothalamic-pituitary-ovarian (HPO) axis: GnRH → FSH/LH → estrogen/progesterone feedback
- Follicular phase: FSH stimulates follicle growth and estrogen production; dominant follicle emerges by Day 7–10
- Ovulation: LH surge (triggered by peak estradiol) causes dominant follicle to rupture; egg released within 36–40 hours
- Luteal phase: ruptured follicle becomes corpus luteum; produces progesterone for 12–14 days
- If no conception: corpus luteum regresses, progesterone falls, endometrium sheds (menstruation), cycle restarts
- Irregular cycles (>35 days or <21 days): primary clinical indicator of ovulatory dysfunction — most commonly PCOS
How does Menstrual Cycle work?
Why does Menstrual Cycle matter in fertility?
The menstrual cycle is the operational framework for all fertility investigation and treatment. Cycle Day 1 is the reference point for all hormonal testing, IVF stimulation start, and embryo transfer timing. Irregular cycles — the most common presenting complaint in fertility practice — signal ovulatory dysfunction, which is the most treatable cause of female infertility (PCOS accounts for ~70% of anovulatory infertility). A woman with regular 28-day cycles is almost certainly ovulating; a woman with cycles of 40–60 days is likely not ovulating in most months. This single clinical observation directs the entire diagnostic and treatment pathway.
What are related terms to Menstrual Cycle?
Follicular Phase
The follicular phase is the first half of the menstrual cycle, beginning on Day …
Ovulation
Ovulation is the release of a mature oocyte (egg) from a dominant ovarian follic…
Luteal Phase
The luteal phase is the second half of the menstrual cycle, beginning at ovulati…
FSH (Follicle-Stimulating Hormone)
FSH (Follicle-Stimulating Hormone) is produced by the pituitary gland. In women,…
LH (Luteinizing Hormone)
LH (Luteinizing Hormone) is produced by the pituitary gland. It triggers ovulati…
Progesterone
Progesterone is a hormone produced by the corpus luteum — the structure left in …
FAQs about Menstrual Cycle
What is a normal menstrual cycle length?
A normal cycle is 21–35 days, measured from Day 1 of one period to Day 1 of the next. The average is 28 days. Cycles shorter than 21 days or longer than 35 days may indicate ovulatory dysfunction.
What does an irregular menstrual cycle mean for fertility?
Irregular cycles often indicate irregular or absent ovulation — the most common cause is PCOS. Without regular ovulation, natural conception is difficult. Most causes of irregular cycles are treatable with medication.
Can stress affect my menstrual cycle?
Yes. Significant psychological or physical stress can disrupt the hypothalamic-pituitary-ovarian axis, causing delayed or absent ovulation. This is usually reversible when the stressor is resolved.
When in the cycle is it possible to get pregnant?
Only during the fertile window — the 5–6 days ending at ovulation. This is typically Days 10–15 in a 28-day cycle, but varies. Intercourse outside this window is very unlikely to result in pregnancy.
How do fertility treatments use the menstrual cycle?
All fertility treatments are anchored to the cycle. Baseline blood tests and scans are done Day 2–3. IVF stimulation starts Day 2–5. Ovulation induction and IUI are timed to the mid-cycle fertile window.
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