How are due dates calculated? The standard calculation is called Nägele’s Rule.  This was developed in the 1850’s by a Dr. Nägele, who determined that the average human pregnancy was 266 days from conception, or 280 days (40 weeks) from the start...

Once you have had your pregnancy confirmed, your pregnancy due date will be worked out from when your last period was. If you do not know for sure when your last period was, you will most likely be asked to make a guess. If you have been planning on getting...