Birth Control Pills

• Birth control pills that are progestin based often cause women to miss a period while on them. These progestin-based pills keep you from ovulating by stopping your ovary from releasing an egg. Besides the commonly noted lack of menstruation, there is also an increased risk of bleeding in between periods for the first few months of use. Some women find that when they discontinue the use of regular birth control pills, they have irregular cycles for up to six months. This will happen until your body resumes its normal hormonal production.
  
  

Polycystic Ovarian Syndrome

• Polycystic Ovarian Syndrome (PCOS) is a condition affecting regular hormonal production in women of childbearing age. PCOS causes a fluctuation and imbalance in androgens (male hormones) and estrogen, which controls the menstrual cycle and ovulation. The main symptom of PCOS is irregular periods. Periods are regulated with the used of low-dose birth control pills, that contain synthetic replacement estrogen and progesterone.
  
  

Endometriosis

• Endometriosis is a condition that only affects women of reproductive age. It is a disorder that causes the endometrium that lines the uterus to grow on the fallopian tubes, ovaries and pelvic tissues. Even thought the endometrial lining is growing outside of the uterus, it still responds as it normally would if it were in the uterus during the menstrual cycle. This causes excessive bleeding that can occur during or in between periods.
  
  

Transitional Menopause

• This stage occurs about two years before the onset of menopause. It can cause the period to become lighter or heavier than usual or change in length. This happens because of changes in the body's production of estrogen. A lack of estrogen initiates menopause. Treatments for menstrual irregularity caused by this are generally short-lived as menopause is pending.
  
  

Postpartum

• After giving birth, it can take up to 45 days to have a regular cycle. After birth, women produce a hormone called prolactin. This hormone is responsible for the production of breast milk. When prolactin is in production, levels of the hormone oestrogen drop, causing the menstrual period to stop. It generally regulates itself within a month, but if you breastfeed, it will take a bit longer.