First, some background on how home pregnancy tests work: Those little sticks detect a hormone called human chorionic gonadotropin (hCG), which is produced when a fertilized egg implants in the uterus.

Today's pregnancy tests are pretty sensitive, rated to detect hCG levels as low as 25 mIU/ml — which women who are pregnant should reach about 10 to 14 days after fertilization, Sullivan says.

Tweaking tries to detect tests taken at even lower levels of hCG, potentially letting women know a week or two weeks sooner than they would if they waited for a missed period and a strong positive test.

But, he adds, "I have to say that while [knowing early] may help anxiety, medically speaking it probably isn't necessary for most people."