A menstrual cycle is, by definition, an ovulatory cycle, where ovulation is the main event and progesterone is made.

Any other kind of bleed is either an anovulatory bleed or a pill-bleed — neither of which are real menstrual cycles. Ovulatory cycles are the only way to make progesterone which is important for women’s general health, and not just for making a baby.

An ovulatory cycle has a follicular phase and a luteal phase. The follicular phase is the pre-ovulatory phase when oestrogen (estradiol) is made. The luteal phase is the post-ovulatory phase when progesterone is made. See graph below.

An anovulatory cycle does not have a luteal phase or progesterone. Instead, it has only a long follicular phase and estrogen and then eventually a breakthrough bleed. See graph below.

Pill-bleeds are not periods. A bleed on the pill is a withdrawal bleed from contraceptive drugs. There’s no ovulation or even attempt at ovulation so there’s no estradiol or progesterone. See graph below.

To sum up;

Ovulation = egg is released = progesterone ✅

Anovulation = no egg released = no progesterone ❌

On the pill = no egg released = no progesterone & no oestrogen ❌

I’ll do another post on progesterone and it’s importance soon 🌟