Late Menstration

A delayed or missed menstruation is the most common pregnancy symptom leading a woman to test for pregnancy. When you become pregnant, your next period should be missed. Many women can bleed while they are pregnant, but typically the bleeding will be shorter or lighter than a normal period.

Other Explanations: Excessive weight gain/loss, fatigue, hormonal problems, tension, stress, ceasing to take the birth control pill, or breast-feeding.