Normal menstrual period occurs every 21 to 35 days and lasts about 5 days. Vaginal bleeding in between periods or intermenstrual bleedingis abnormal. Vigorous exercise, unless resulting in undue stress, is perhaps not the reason for the bleeding.
Most cases of intermenstrual bleeding are due to non-cancerous and treatable causes. Occasionally, it may be due to cancer or pre-cancer. Thus it has to be assessed and treated promptly. Common causes of intermenstrual bleeding include:
Pregnancy complications: Miscarriage and ectopic pregnancy.
Hormonal imbalance from emotional or work-related stress.
Cervical or endometrial polyps: These are benign or non-cancerous growths in the cervix (neck of womb) or lining of the womb.
Hormonal contraception: Irregular bleeding can happen during the first three months of taking hormonal contraception in the form of pills, vaginal rings, skin patches, implants or injections.
Infection of the cervix from sexually transmitted diseases.
Uterine fibroid: This is a muscle growth of the womb. It it protrudes into the uterine cavity, it can cause heavy and irregular bleeding.
Polycystic ovary syndrome (PCOS): The irregular or absent ovulation in this condition may result in irregular bleeding.
Cervical cancer or pre-cancer may cause irregular bleeding, especially bleeding after sex.
Uterine cancer: this is more common in older women, who may present with abnormal bleeding during menopause.