When we start talking about the length of pregnancy and the age of the baby it can sometimes become confusing to mothers because they fully understand how we calculate dates. There are two terms used sometimes.

One is gestational age. That is the calculation that most doctors use to calculate due date and it's based on the first day of your last menstrual period. It technically includes approximately two weeks where the woman was not pregnant.

The fetal age is another term that refers to the actual age of the baby starting at the time of conception. So typically fetal age is going to be two weeks less than gestational age.

The reason we do it that way is it's important to have concrete dates to determine when we do certain tests during the pregnancy. Gestational age is the easiest way to do that.

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