Breakthrough bleeding: is it your period or something off about your period? Turns out that it’s tricky It’s bleeding that seems like your period, but it’s not. You may think that if you have period-like bleeding, then you definitely ovulated earlier that cycle. But this is not necessarily true.
If you’re getting a regular menstrual period, it most likely means that ovulation also happens regularly. Women who track their cycles closely know that if ovulation is delayed for some reason, it usually means that menstruation will be delayed, too (that’s why we sometimes say that there’s no such thing as a late period).
But it’s also possible to have an anovulatory cycle, or a cycle where you don’t ovulate, but you still get your period. When this happens, you may experience breakthrough bleeding, which seems like a normal period, but technically is a bit different.
What causes bleeding when I don’t ovulate?
To explain this, we have to revisit the hormones of the menstrual cycle. In a normal menstrual cycle, estradiol (the main estrogen hormone) increases steadily during the first half of the cycle. Estradiol helps to build up the uterine lining. Increasing estrogen levels help to trigger ovulation, which is the release of an egg from a follicle in the ovaries. After ovulation, the spent follicle transforms into something called a corpus luteum, which secretes the hormone progesterone. Progesterone levels are high during the second half of the cycle. This is important because one of the primary purposes of progesterone is to provide structure for the uterine lining built up earlier in the cycle.
If the egg is not fertilized, then the corpus luteum shrinks and stops secreting progesterone. Without progesterone maintaining the uterine lining, it can no longer be maintained within the uterus, so it sheds in the process you will recognize as your period.
If you did not ovulate, no corpus luteum is formed, and no progesterone is secreted. So, while the first half of your cycle was spent building up the uterine lining, there isn’t a hormone signal for maintaining it without ovulation. The uterine lining still has to be shed, and you can still experience bleeding that looks similar to your period. Although scientists still don’t understand exactly why this extra tissue needs to be shed, one possible explanation is that building and supplying the uterine lining with new blood vessels requires a considerable amount of extra energy. Without a reason to sustain it (like implantation), the unnecessary tissue breaks down to conserve energy, which leads to bleeding and resetting the next cycle.
Nonetheless, breakthrough bleeding is NOT the same as your period. Menstruation is bleeding that results from a drop in progesterone. Breakthrough bleeding of this type results from a drop in estrogens.
The take-home message: it is possible to experience bleeding during your cycle whether you ovulate or not. So, if you’re trying to track your ovulation and don’t observe a biphasic temperature shift, you may still experience breakthrough bleeding because of an anovulatory cycle.
Why does anovulation happen?
Anovulatory cycles seem to be most common when the body is adjusting after a major change in hormones. Women may experience these cycles when they first begin menstruating, are coming off the pill, have just given birth, or are approaching menopause.
But, you can still experience a few anovulatory cycles outside of these times because factors like stress1 or suddenly beginning a vigorous workout schedule2 can temporarily disrupt ovulation. Chances are every woman will experience a few cycles of anovulation at some point in her life.
However, if you experience recurrent anovulatory cycles, then it is important to talk to your doctor. Recurrent anovulation can be a sign of polycystic ovarian syndrome (or PCOS), or when ovarian cysts cause hormone imbalance and irregular cycles. If you’re concerned that you may have PCOS, talk to your doctor about getting tested for it.
Is breakthrough bleeding the same as implantation bleeding?
If you’re trying to conceive and observe some spotting, you might wonder if it’s breakthrough bleeding or implantation bleeding. However, there is no evidence that implantation bleeding happens. Spotting is more likely to indicate you’re not pregnant than you are.