Gestational Age Is the reference traditionally used by medical providers to date your pregnancy. This refers to how long it’s been since the first day of your last period. It is also referred to as the last menstrual period (LMP).
The gestational age begins about two weeks before the sperm fertilises the egg.
Fertilisation age Refers to how long it’s been since conception: the fertilization of the egg by the sperm. Most women ovulate in the middle of their monthly cycle. For example , if you have a 28 day cycle you would typically ovulate around the 14th day after your last period. If the sperm fertilizes your egg, a new life begins and this becomes the first fertilization day.