Here's why you should stop using HPTs at 6 weeks

Listen up, ladies! (Sorry, I love-hate that phrase.) Since we're in the May babies group, now is the perfect time to talk about the "hook effect" regarding home pregnancy tests, and why testing urine 5-7 weeks after your LMP can cause undue worry.

It's true that hCG steadily rises throughout the first 9-10 weeks of pregnancy, then declines and plateaus after your placenta takes over hormone production. But there are actually several variants of hCG that show up in different concentrations in different places in your body (i.e. urine vs blood serum) at different times during pregnancy. One of these variants, hCG beta core fragment, can show up in very high concentrations in your urine starting at between 5-7 weeks. A *majority* of HPTs, including a majority of the urine pregnancy tests used by clinicians, do not properly react with hCG-bcf. This results in a declining intensity in the color of your test line as you progress beyond 5 weeks. Some HPTs will straight up give you a false negative after 7+ weeks!

This isn't true for all tests - some of them are sensitive to hCG-bcf and continue to show a strong positive result after 6 weeks. But most won't. So the best bet is to stop testing urine by 6 weeks - in fact, doctors should only be confirming a pregnancy with quantitative b-hCG in blood serum and/or by ultrasound at that point.

I hope this helps ease any worries about lines getting less dark between 5-7 weeks for any fellow POAS addicts out there. The research on the hook effect is growing, and there are already calls for the FDA to update their regulations on hpt packaging and inserts to reflect their progressive inaccuracy. Sticky beans, everyone!