Originally Posted by Chesby05

Yes they are different by two weeks - give or take a few days. Gestational age is taken from the first date of your LMP (last menstrual period) and that's what makes pregnancy 40 weeks when it is `technically' 38. Ovulation takes place approximately 14 days after the first date of your LMP, which is why gestational age is nearly always two weeks more than the date of conception.

For example, the first date of my LMP was October 13, so my foetus's gestational age is 25 weeks and a few days. However my date of conception was the October 27, so her `foetal age' is 23 weeks and a few days. In medical terms though, things are always done by gestational age.

Those websites go by gestational age, because that is how your pregnancy is defined by your doctors and medical care. So to say that a foetus opens its eyes at 28 weeks actually means 26 weeks after conception - does that make sense? I don't know why they do it that way, but there must be a good reason!! Lol.....