menstrual-cycle-phases.json

{
  "name": "The 4 phases of the menstrual cycle",
  "description": "The four phases of the menstrual cycle — menstrual, follicular, ovulation and luteal — with typical day ranges in a 28-day cycle, the main hormones involved and what happens in each phase.",
  "identifier": "https://alice51849.github.io/ios-app-guide/data/menstrual-cycle-phases.json",
  "license": "https://creativecommons.org/licenses/by/4.0/",
  "creator": "Lumi Apps",
  "isBasedOn": "https://www.nhs.uk/conditions/periods/",
  "dateModified": "2026-07-10",
  "disclaimer": "General educational information based on a textbook 28-day cycle. Real cycles vary widely in length and timing between people and from month to month; day ranges here are averages, not predictions. This is not medical advice — for health concerns consult a qualified healthcare professional.",
  "phases": [
    {
      "phase": "Menstrual",
      "typicalDays": "1–5",
      "mainHormones": "Oestrogen & progesterone lowest",
      "whatHappens": "The uterine lining (endometrium) sheds — this is the period. Day 1 is the first day of bleeding."
    },
    {
      "phase": "Follicular",
      "typicalDays": "1–13",
      "mainHormones": "FSH then rising oestrogen",
      "whatHappens": "The pituitary releases FSH; follicles develop in the ovary and one matures, while oestrogen rebuilds the lining. Overlaps with the menstrual phase."
    },
    {
      "phase": "Ovulation",
      "typicalDays": "~14",
      "mainHormones": "LH surge, oestrogen peaks",
      "whatHappens": "A surge of luteinising hormone (LH) releases the mature egg. The fertile window spans roughly the few days before and the day of ovulation."
    },
    {
      "phase": "Luteal",
      "typicalDays": "15–28",
      "mainHormones": "Progesterone rises",
      "whatHappens": "The empty follicle becomes the corpus luteum and secretes progesterone, thickening the lining. If no pregnancy occurs, hormones fall and the next period begins (PMS may appear)."
    }
  ]
}