One of the complaints about the Georgia HeartBeat Abortion Law, which bans abortion from the time that a doctor can detect a heartbeat, is that it begins supposedly “before most women know they are pregnant”, at what the media is calling “six weeks” into pregnancy. It is true?
“The cardiovascular system is the first organ system to reach a functional state. The embryonic heartbeat can be detected using Doppler ultrasonography during the fourth week, approximately 6 weeks after the last normal menstrual period….” 
There are two ways to count the length of time into a pregnancy, from last normal menstrual period (LNMP) and from fertilization. Since fertilization occurs about two weeks after LNMP, the difference between the two ways to count is 2 weeks. A heartbeat is detectible during week 4 from fertilization, about 6 weeks after LNMP.
A 2006 article published in the Journal of Obstetric, Gynecologic, & Neonatal Nursing considered four past studies along with its own study. The average cycle length across all five studies was 28.5 days and 95% of cycles fell within a range of 22 to 35 days. 
When does a woman know she is pregnant? Her next period would be expected, depending on the usual length of her cycle, about 22 to 35 days later. Average cycle length is 28.5, so on average a woman begins to suspect she has missed her next period about 4 weeks, and as long as 5 weeks, after her last period began. But the fetal heartbeat does not begin until 6 weeks after LNMP.
And when a woman suspects she is pregnant, she can take a home pregnancy test, which at that point can detect pregnancy. The tests can identify pregnancy two weeks after fertilization, which is 4 to 5 weeks after LNMP. So if a woman thinks she has missed per period, she can take a test and determine if she is pregnant.
“Enough hCG is produced by the syncytiotrophoblast at the end of the second week to give a positive pregnancy test….” 
Can pregnancy be detected any earlier? Yes, with a lab test for EPF, pregnancy can be detected 24 to 48 hours after fertilization.
“Early pregnancy factor, an immunosuppressant protein, is secreted by the trophoblastic cells and appears in the maternal serum within 24 to 48 hours after fertilization. Early pregnancy factor forms the basis of a pregnancy test during the first 10 days of development.” 
But this is an unusual test. The common test is for hCG, which works 2 weeks or more after fertilization.
In any case, 6 weeks after LNMP is when the heartbeat begins to be detectable. It is also a week or two after her next period would be expected. A woman who is sexually active and a week or two “late” should know to take a home pregnancy test, or to see her healthcare provider.
So it is not true that the Georgia HeartBeat Bill HB481 outlaws abortion “before most women know they are pregnant.”
 Moore, Keith L.. The Developing Human E-Book: Clinically Oriented Embryology . Elsevier Health Sciences. Kindle Edition.
 Fehring, Richard J., Mary Schneider, and Kathleen Raviele. “Variability in the phases of the menstrual cycle.” Journal of Obstetric, Gynecologic & Neonatal Nursing 35.3 (2006): 376-384.