What is oligomenorrhea?
Oligomenorrhea is the medical term for infrequent periods: menstrual cycles that are regularly longer than 35 days, or fewer than about 9 periods in a year. It often means ovulation is happening less often. It is common in the first years after a first period and in perimenopause, and polycystic ovary syndrome is a frequent cause.
Common causes
- PCOS, the most common cause in adults
- Puberty and perimenopause, when ovulation is less regular
- Low energy availability from intense exercise, under-eating or big weight loss (hypothalamic amenorrhea at the extreme)
- Thyroid problems or high prolactin
- Breastfeeding, and some medicines
- Coming off hormonal contraception
Why it matters
Long gaps between periods can make it harder to conceive, because ovulation is less frequent and harder to predict. If periods are very infrequent for a long time, the uterine lining is exposed to estrogen without regular shedding, which doctors like to prevent. So it's worth finding the cause.
Related terms
Periods that come too often are polymenorrhea. No period for 3 months or more is secondary amenorrhea. See the full guides to long cycles and irregular periods.
Long, unpredictable cycles can make PMS feel like it arrives out of nowhere. Tracking mood daily helps you spot the run-up to a period even when the date is uncertain.
See a doctor if your cycles are regularly longer than 35 days, you have fewer than 9 periods a year, or you also notice excess hair, acne or weight changes.
Frequently asked questions
Is a 40-day cycle oligomenorrhea?
Cycles regularly longer than 35 days fit the definition. One long cycle now and then is common and usually not a concern.
Can you get pregnant with oligomenorrhea?
Yes, as long as you ovulate sometimes. Ovulation tests or temperature tracking help find when. A doctor can help if it's taking a while.
Sources
This page is for information only and isn鈥檛 medical advice. If something worries you, please talk to a doctor.
Keep reading
Long menstrual cycle: what it means if your cycle is over 35 daysLong menstrual cycle over 35 days? Why ovulation comes late, common causes like PCOS, stress and thyroid, what a 40 or 45 day cycle means, and what helps.What is PCOS (polycystic ovary syndrome)?PCOS (polycystic ovary syndrome) is a common hormone condition causing irregular periods, high androgens and ovulation problems. Signs, diagnosis and care.What is secondary amenorrhea?Secondary amenorrhea means your periods stop for 3 months or more after you've had them before. Common causes, tests, and when to see a doctor.Irregular periods: definition and meaningIrregular periods means cycle lengths that vary a lot from month to month, or cycles shorter than 21 or longer than 35 days. Causes and when to get checked.Is a 40-day cycle normal?Is a 40 day cycle normal? For teens and some adults it can be, but it's outside the usual 21 to 35 days. Common causes, ovulation timing, and when to ask.