What do systematic reviews say?

Progestogen therapy long cycle (3 to 4 weeks) vs other medical therapy

Progestogen therapy long cycle (3 to 4 weeks) showed no clear difference in adverse effect Headache compared with other medical therapy (low certainty).

• Cyclical progestogens for heavy menstrual bleeding 2019 · Cochrane Headline outcomes only
  OR 1.45 [0.4, 5.31]
  2 studies · 189 participants
  Low