Key point: Irregular periods usually indicate irregular or absent ovulation — which significantly affects your ability to conceive. But the underlying causes are almost always treatable. The first step is finding out why your cycles are irregular.
A normal menstrual cycle lasts between 21 and 35 days, is reasonably predictable in length (varying by no more than 7–8 days cycle to cycle), and includes 3–7 days of bleeding. If your cycle falls consistently within this range, it is considered regular — even if it's not exactly 28 days.
Irregular periods are those that consistently fall outside this range, vary significantly from cycle to cycle, or are absent for months at a time.
| Cycle Pattern | Likely Meaning | Fertility Impact |
|---|---|---|
| 21–35 days, consistent | Normal | Minimal |
| Cycles 35–60 days | Oligomenorrhoea — likely PCOS or thyroid | Reduced ovulation frequency |
| Cycles >60 days or <6/year | Severe oligomenorrhoea — PCOS, POI | Very few fertile windows |
| No periods (amenorrhoea) | Absent ovulation — multiple causes | Natural conception not possible |
| Highly variable lengths (20–45 days) | Irregular ovulation — stress, thyroid, PCOS | Difficult to time conception |
Fertility depends on ovulation — the monthly release of an egg from the ovary. Most irregular menstrual cycles are caused by irregular or absent ovulation (anovulation). If ovulation doesn't happen, there is no egg available for fertilisation, regardless of how perfect everything else is.
Even when ovulation does occur in a woman with irregular cycles, not knowing when it happens makes timed intercourse very difficult. A woman with 40–50 day cycles may ovulate on Day 25–35 — far beyond the standard Day 14 that most apps and advice assume.
The most common cause — responsible for approximately 70–80% of irregular period cases. In PCOS, elevated LH and androgens disrupt follicle maturation, preventing regular ovulation. Cycles are often 35–60+ days, and some women have fewer than 6 periods per year.
Both underactive (hypothyroidism) and overactive (hyperthyroidism) thyroid glands disrupt menstrual regularity. Hypothyroidism commonly causes heavy, irregular periods, while hyperthyroidism can cause light or absent periods. Thyroid disorders are very common in Indian women and often undiagnosed.
Prolactin is the hormone that stimulates milk production after childbirth. When prolactin is elevated without pregnancy (sometimes due to stress, medication, or a benign pituitary microadenoma), it suppresses ovulation and causes irregular or absent periods. Treatment with cabergoline restores normal cycles.
As ovarian reserve declines, cycles may shorten initially (cycles of 21–25 days are common in early ovarian insufficiency) and then become irregular. If you are under 40 with cycle changes, early ovarian insufficiency should be evaluated.
Significant weight loss, extreme exercise (common in athletes), chronic stress, or very low BMI can all suppress the hypothalamic-pituitary axis and stop ovulation. This is called functional hypothalamic amenorrhoea and is reversible with lifestyle modification.
See a fertility specialist if:
At Mother Hospitals, our evaluation for irregular cycles typically includes:
Treatment depends on the cause:
Don't wait and hope: Irregular periods rarely resolve spontaneously when they are due to a hormonal condition. Getting evaluated early means more treatment options and better outcomes. Most causes are completely treatable.
Dr. Prashanthi Reddy provides complete menstrual and fertility evaluations at Mother Hospitals, Boduppal. Find out the cause and get a personalised treatment plan.
Book Your Consultation