The Menstrual Cycle
Every month your body goes through 4 phases. Here’s exactly what’s happening.
Did you know your body goes through four distinct phases every single month? Whether your cycle is 28 days or 35 days, the same hormonal journey plays out – your brain and ovaries working together in a carefully timed sequence.
Let’s break it all down, phase by phase, in simple language.
Phase 1: The Period (Days 1–5)
Also called: The Menstrual Phase
Your cycle officially begins on Day 1 – the first day of your period. The uterus sheds its lining because no fertilised egg arrived last month.
But here’s the fascinating part: while your period is happening on the outside, your brain is already quietly planning ahead. Your pituitary gland releases a hormone called FSH (Follicle-Stimulating Hormone), which acts as a “wake-up call” to tiny egg sacs (called follicles) in your ovaries, telling them to start growing.
Think of it like this: while your body is clearing out last month’s lining, it’s already planting seeds for next month. Multi-tasking at its finest!
Phase 2: The Build-Up (Days 6–13)
Also called: The Pre-Ovulatory or Follicular Phase
Several follicles start growing in response to FSH, but only one will become the “winner.” Here’s how it plays out:
- One follicle grows faster than the rest and becomes the dominant follicle which is going to release an egg.
- That winning follicle pumps out oestrogen.
- The dominant follicle also releases a hormone called inhibin, which tells the brain: “Stop sending FSH — I’m the only follicle you need now.” This quietly shuts down the other follicles.
Think of it like this: The dominant follicle is like a contestant who wins the competition AND quietly unplugs everyone else’s microphone.
Phase 3: The Big Release (Day 14)
Also called: Ovulation
This is the main event and it all happens in a matter of hours. This is the only time in the entire cycle when pregnancy is possible.
Oestrogen keeps rising until it hits a peak. When it gets high enough, something unusual happens: instead of telling the brain to slow down (like most hormones do), high oestrogen triggers a massive surge of LH (Luteinising Hormone). Think of LH as the “launch signal.”
The LH surge causes the follicle to burst open and release the egg. The egg then travels down the fallopian tube. This is ovulation.
The empty follicle doesn’t disappear. It transforms into a new structure called the corpus luteum i.e. a temporary hormone factory that’s about to become very important.
Think of it like this: High oestrogen is like pressing a button that fires a rocket (LH). The rocket blasts open the follicle and launches the egg. The launchpad then rebuilds itself into something entirely new.
Phase 4: The Waiting Game (Days 15–28)
Also called: The Post-Ovulatory or Luteal Phase
This is the longest phase (roughly two weeks) and your body spends it holding everything in readiness, just in case.
The corpus luteum produces progesterone which keeps the uterus lining thick and welcoming, perfect for a fertilised egg to implant.
- If a fertilised egg arrives and implants: pregnancy begins! The corpus luteum keeps producing progesterone to support the early pregnancy.
- If no egg implants: the corpus luteum breaks down. Progesterone and oestrogen levels drop. The uterus lining sheds and your period starts, beginning the whole cycle again from Day 1.
Think of it like this: The corpus luteum is like a hotel keeping a room prepared for a guest. If the guest (fertilised egg) arrives, the hotel stays open. If not, it closes down and the whole hotel resets for next month.
Quick Summary
- Days 1–5 (Menstrual Phase): Lining sheds, FSH rises, follicles start growing.
- Days 6–13 (Follicular Phase): One follicle dominates, oestrogen rises, uterus lining thickens.
- Day 14 (Ovulation): LH surge triggers egg release. Corpus luteum forms.
- Days 15–28 (Luteal Phase): Progesterone maintains lining. Period returns if no pregnancy.
A typical cycle lasts 21–35 days. The second half (after ovulation) is almost always 14 days — it’s the first half that varies. That’s why tracking ovulation can help you predict your period more accurately.