Definitions of early pregnancy

Gestational age (also called menstrual age or menstrual dating) is estimated in completed days or weeks from the date of the woman's last menstrual period (LMP). Ovulation is assumed to occur two weeks after the LMP. Accurate menstrual dating depends upon knowledge of LMP and regular 28-day cycle length and is considered to have an accuracy of ±2 weeks. Embryonic or fetal age is calculated from the presumed date of ovulation and is therefore two weeks less than gestational age measured from the LMP.

The first trimester of pregnancy corresponds to a gestational age of < 14 weeks. Early pregnancy is typically defined as <10 weeks' gestation. The following table offers synonymous terms used to describe gestational ages in the first trimester of pregnancy.


 
Gestational age (days)
Gestational age (weeks)
Embryonic age
Very early pregnancy
< 42 days
< 6 weeks
< 4 weeks
Very early pregnancy
< 49 days
< 7 weeks
< 5 weeks
Early pregnancy
< 56 days
< 8 weeks
< 6 weeks
Early pregnancy
< 63 days
< 9 weeks
< 7 weeks


If you have questions about medication abortion, please visit our frequently asked questions section.