The standard calculation is called N gele s Rule. This was developed in the 1850 s by a Dr. N gele, who determined that the average human pregnancy was 266 days from conception, or 280 days (40 weeks) from the start of the last menstrual period. To calculate this, begin with the first day of your last period (LMP).Add 7 days, then subtract 3 months.f ultrasound is performed in the first trimester, it can indicate fetal age within a range of 3 5 days. Later in pregnancy, it is less accurate. Up to 20 weeks, the margin of error is 7 10 days. By the third trimester, an ultrasound date can be off by as much as 3 weeks in either direction.
The common cold (also known as nasopharyngitis, rhinopharyngitis, acute coryza, head cold, or simply a cold) is a viral infectious disease of the upper respiratory tract which primarily affects the nose.
Introduction. A cold is an upper respiratory infection caused by a virus. Colds tend to occur most often in winter, although scientists aren't sure why. In the United States, adults usually have 2 colds per year, and children have at least 6.ntroduction. A cold is an upper respiratory infection caused by a virus. Colds tend to occur most often in winter, although scientists aren't sure why. In the United States, adults usually have 2 colds per year, and children have at least 6.