Anovulatory Cycles: Causes, Breakthrough Bleeding, and Concerns

Breakthrough bleeding: is it your period or something else? It turns out it’s not straightforward. It resembles your period but isn't quite the same. You might assume that period-like bleeding indicates ovulation earlier in the cycle, but that’s not always the case.

Generally, having a regular menstrual period suggests regular ovulation. Women who closely track their cycles know that a delay in ovulation usually means a delayed menstruation (hence, the idea that a "late period" doesn't really exist).

However, it’s possible to experience an anovulatory cycle—one where you don't ovulate but still bleed. In such cases, you might have breakthrough bleeding, which appears like a normal period but is technically different.

Why do I bleed without ovulating?

To understand this, we need to revisit menstrual cycle hormones. In a typical cycle, estradiol (a primary estrogen) increases steadily during the first half, helping build the uterine lining. Rising estrogen levels trigger ovulation, releasing an egg from an ovarian follicle. Post-ovulation, the follicle transforms into the corpus luteum, which secretes progesterone. Progesterone is crucial during the second half of the cycle for maintaining the uterine lining.

If the egg isn’t fertilized, the corpus luteum shrinks, halting progesterone secretion. Without progesterone, the uterine lining can’t be maintained and sheds, resulting in your period.

In an anovulatory cycle, no corpus luteum forms, so no progesterone is produced. Although the uterine lining builds up in the first half of the cycle, without ovulation, there's no signal to maintain it. The lining still needs to be shed, causing bleeding that looks like your period. While the exact reason for shedding this extra tissue is unclear, one theory is that maintaining the uterine lining with new blood vessels requires significant energy. Without a need to sustain it (such as for implantation), the tissue breaks down to conserve energy, leading to bleeding and resetting the cycle.

However, breakthrough bleeding differs from menstruation. Menstruation results from a drop in progesterone, while breakthrough bleeding stems from a drop in estrogen.

The key takeaway: It’s possible to experience bleeding in your cycle whether or not you ovulate. So, if you’re tracking ovulation and don’t see a biphasic temperature shift, you may still have breakthrough bleeding due to an anovulatory cycle.

Why does anovulation occur?

Anovulatory cycles are common when the body adjusts to significant hormonal changes. Women may experience these cycles when they first start menstruating, come off the pill, recently give birth, or approach menopause.

Anovulatory cycles can also occur outside these times due to factors like stress or sudden intense exercise, which can temporarily disrupt ovulation. Most women will experience a few anovulatory cycles at some point.

If recurrent anovulatory cycles occur, it’s important to consult us at Calm Fertility Care or another provider of Restorative Reproductive Medicine. Recurrent anovulation can indicate conditions like polycystic ovarian syndrome (PCOS), where ovarian cysts cause hormonal imbalances and irregular cycles. If you’re concerned about PCOS, talk to your doctor about testing.

Is breakthrough bleeding the same as implantation bleeding?

If you’re trying to conceive and notice spotting, you might wonder if it’s breakthrough bleeding or implantation bleeding. However, there’s no evidence that implantation bleeding occurs. Spotting is more likely a sign that you are not pregnant than that you are.