When it comes to the menstrual cycle, many people assume that a period means ovulation happened. But that’s not always true. You can have menstrual bleeding without ovulating - a phenomenon known as anovulatory cycles.

So, if menstruation is day 1 of the cycle, does that mean it comes first? Or does ovulation actually drive the process? Let’s break it down.

The Menstrual Cycle: What Happens First?

A new cycle begins with menstruation - this is day 1. But the reason you have a period (in a typical cycle) is because ovulation already happened in the previous cycle.

Here’s how it works:

Follicular Phase (Before Ovulation) – The body prepares to release an egg by increasing follicle-stimulating hormone (FSH) and estrogen.
Ovulation (Mid-Cycle) – A surge in luteinizing hormone (LH) triggers ovulation, releasing an egg from the ovary.
Luteal Phase (After Ovulation) – The empty follicle (corpus luteum) produces progesterone, which stabilizes the uterine lining in preparation for a potential pregnancy.
Menstruation (If No Pregnancy) – If no fertilization occurs, progesterone drops, leading to the shedding of the uterine lining.

But What If You Don’t Ovulate?

If ovulation doesn’t happen, the hormonal pattern shifts. Without ovulation, there’s no corpus luteum to produce progesterone. Instead, estrogen builds up, and the uterine lining may eventually shed - but this isn’t a true period. This is known as anovulatory bleeding, and it can be irregular, heavy, or unpredictable.

What Is Anovulation?

Anovulation occurs when the ovaries don’t release an egg during a menstrual cycle. It’s a leading cause of infertility, contributing to 20–25% of infertility cases.

📌 Key Signs of Anovulation:

Irregular or long cycles (often >35 days)
Absent or unpredictable periods
Very light or very heavy bleeding
No clear mid-cycle LH surge or temperature shift (for those tracking ovulation)

Not all cases of anovulation are obvious, and some people may have regular-appearing periods despite not ovulating.

What Causes Anovulation?

Anovulation can result from various factors, including:

1. Hormonal Imbalances

Polycystic ovarian syndrome (PCOS) – One of the most common causes, leading to irregular cycles due to excess androgens and insulin resistance.
Thyroid disorders – Hypothyroidism or hyperthyroidism can disrupt ovulation.
High prolactin levels (hyperprolactinemia) – Can interfere with ovulation and cause irregular or even missed periods.

2. Lifestyle and Metabolic Factors

Extreme stress – Disrupts signals between the brain and ovaries.
Poor diet and nutrition deficiencies – Can impact hormone production.
Excessive exercise – Common in athletes, leading to hypothalamic amenorrhea.

3. Genetic and Chronic Health Conditions

Family history of reproductive issues or genetic predispositions
Metabolic disorders affecting insulin or energy balance

Why Ovulation Matters (Even Beyond Fertility)

Even if you’re not trying to conceive, ovulation is important for overall health.

Regular ovulation supports:

Hormonal balance – Keeps estrogen and progesterone levels in check which are important for mood, energy, and reproductive health.
Bone health – Progesterone and estrogen help maintain bone density. Anovulation can increase the risk of osteoporosis over time.
Metabolic function – Regular cycles are linked to better insulin sensitivity and a reduced risk of developing metabolic conditions like Type 2 diabetes.
Mood and cognitive function – Hormonal stability from regular ovulation can improve mental well-being, reducing the risk of mood disorders like depression and anxiety.

Long-term anovulation can increase the risk of more severe conditions, including cardiovascular disease, endometrial hyperplasia (thickening of the uterine lining), and even endometrial cancer due to prolonged exposure to estrogen without the balancing effects of progesterone.

How Can You Track Ovulation?

To check if you’re ovulating, you can monitor:

Ovulation predictor kits (OPKs) – Detect LH surges.
Basal body temperature (BBT) – After ovulation, your BBT rises slightly and stays elevated until your period starts. A consistent temperature shift is a reliable sign of ovulation.
Cervical mucus changes – Before ovulation, cervical mucus changes to a clear, stretchy, egg-white consistency, signaling peak fertility.

For individuals with irregular cycles or suspected anovulation, blood tests to check progesterone levels (typically on day 21 of the cycle) can confirm whether ovulation has occurred.

How Is Anovulation Treated?

Treatment depends on the cause:

Lifestyle changes – Reducing stress, improving nutrition, and ensuring moderate exercise can restore ovulation, especially in cases of functional hypothalamic anovulation.
Medical treatment – Clomiphene citrate or letrozole are commonly prescribed to stimulate ovulation. Gonadotropins may also be used for more resistant cases.
Hormonal therapy – For those with conditions like PCOS, regulating cycles with hormonal treatments such as birth control pills can help normalize cycles, though they won’t result in ovulation.

If anovulation is linked to PCOS or thyroid disorders, addressing the underlying condition can help restore ovulation.

Final Thoughts: What Comes First?

Technically, menstruation starts the cycle (day 1), but ovulation is what drives a healthy cycle. If ovulation doesn’t occur, you may still experience anovulatory bleeding, but it’s not a true period.

If you suspect anovulation, tracking your cycle and consulting a healthcare professional can provide clarity.

DISCLAIMER: THIS BLOG POST DOES NOT PROVIDE MEDICAL ADVICE

The information in this blog post, including but not limited to the text, graphics and images, are for educational and informational purposes only. None of the material within this blog post is intended to substitute medical advice, diagnosis or treatment. Always seek the advice of a qualified medical professional such as your doctor when you have concerns or questions.

References & Further Reading

Bhandoria, G., & Rudra, S. (2013). Anovulatory Infertility: A Prospective Study. International Journal of Infertility and Fetal Medicine, 4(1), 18–23. https://doi.org/10.5005/JP-JOURNALS-10016-1055

Gavina, B. L. A., de los Reyes, A. A., Olufsen, M. S., Lenhart, S., & Ottesen, J. T. (2022). Toward an optimal contraception dosing strategy. bioRxiv, 19. https://doi.org/10.1101/2022.04.04.486926

Kumari, S., & Dave, H. (2024). Management of Infertility due to Anovulation (Beejadusti Janya Stri Vandhyatwa) by Ayurvedic Regime. Ayushdhara, 160–165. https://doi.org/10.47070/ayushdhara.v11i4.1695

What Comes First, the Egg or the Period?