They say 20% of pregnancies end in miscarriage. are they including the really early ones that happen before you know your pregnant?

Miscarriages ?: Statistically about 20 % or even more of pregnancies may be miscarriages, but most of those may be by early pregnancies. First actual pregnancies often go unnoticed except for minor delays in the onset of a period. Genetic abnormalities or rejection of foreign protein by maternal anti-HLA antibodies may cause very early cessation of pregnancy.