We all know that PCOS can cause irregular periods, but I know a 27-year-old girl who has always had regular periods, although her bleeding usually lasted only 1–2 days. For the last three cycles, however, she has been bleeding for only 2–3 hours and then it completely stops. All her blood reports are normal. What could be the reason for such a sudden change in her menstrual flow?
sudden change from an already-light period to bleeding for only a few hours can happen for several reasons, and PCOS is not the only possibility.
Some possibilities include:
Temporary hormonal/ovulation changes, even if her previous cycles were regular.
Stress, significant weight loss/gain, excessive exercise, or changes in sleep can affect menstrual flow.
Pregnancy-related bleeding can sometimes be mistaken for a very light period, so a pregnancy test is worth doing if pregnancy is possible.
Hormonal contraception (including pills, injections, implants or hormonal IUDs) can make periods much lighter or stop them.
Thyroid or other hormonal problems can also alter the menstrual pattern, even when routine blood tests are normal.
Since this has happened for three consecutive cycles, I wouldn't simply assume it is PCOS. A gynaecologist can review her cycle history, medications, pregnancy possibility and, if needed, check hormone levels and do a pelvic ultrasound. A change from her usual pattern that persists is worth evaluating.