Potentially detect early signs of pregnancy ; Related: The Best Basal Thermometers to Help You Kick-Start Your Family Planning Journey . Choosing a BBT Chart.

The "most sensitive" drugstore tests can detect pregnancy as early as three or four weeks after your period date, Tang says. In those first few weeks, pregnancy hormones are on the rise every day.

HCG is often the first indicator of pregnancy – it's what causes a positive result on a home pregnancy test. HCG levels rise ...