Trying to Conceive With Irregular Periods

Guides. Updated October 11, 2026. Calculated with the standard pregnancy dating method used by ACOG and the NHS.

Calendar calculators work best with regular cycles. If your cycle length varies by more than a week from month to month, ovulation is harder to predict.

Ways to find ovulation

Ovulation tests, cervical mucus observations and temperature charting all track what is happening in the current cycle rather than relying on averages.

Covering the window

Having sex every two to three days throughout the cycle means you will not miss the fertile window, without needing to pinpoint it.

When to get checked

Very irregular, very long or absent periods can mean ovulation isn't happening regularly. Conditions such as PCOS and thyroid problems are common and treatable, so it's worth seeing a doctor.

This article is general information, not medical advice. Talk to a doctor or midwife about your own pregnancy or fertility.