Fifty percent of the total mass of the atmosphere is located in the lower 5.6 km (18,000 ft) of the troposphere. It is primarily composed of nitrogen (78%) and oxygen (21%) with only small concentrations of other trace gases.
Having irregular periods is very common. I see them in my practice all the time. The causes can range from something insignificant to something that requires treatment. For example, if you're a teen, your body's hormones can fluctuate and take some time until they find a balance.
About Irregular Periods and Pregnancy. A regular period is defined as a 25  31 day cycle from the start of one period to the next, with three to five days of bleeding. Irregular periods are considered anything that diverges from the regular menstrual cycle.bout Irregular Periods and Pregnancy. A regular period is defined as a 25  31 day cycle from the start of one period to the next, with three to five days of bleeding. Irregular periods are considered anything that diverges from the regular menstrual cycle.