Referring to a fetus.
Age of the conceptus counted from the time of fertilization. Since in most cases pregnancy is counted from the first day of the last menstrual period but fertilization occurs about 2 weeks thereafter, the fetal age is often about 2 weeks less than the calculated length of the pregnancy. Also called fertilization age.
The term “fetus” pertains to the developing offspring, also recognized during the initial two months following conception as an embryo.