When it comes to bleach pregnancy tests, the science behind them is based on the chemical reaction that occurs between bleach and the hormones present in a woman's urine when she is pregnant. The idea is that when bleach comes into contact with urine containing the hormone human chorionic gonadotropin (hCG), which is produced by the placenta after implantation, it will cause a fizzing or foaming reaction.

However, it's important to note that bleach pregnancy tests are not scientifically proven or reliable. The reaction between bleach and hCG is not specific to pregnancy, and other substances can also cause fizzing when mixed with bleach. Additionally, the concentration of hCG in urine may not be high enough to produce a noticeable reaction with bleach, leading to false negative results.

It's always best to use medically approved and scientifically validated pregnancy tests, such as those that detect hCG in urine through specific antibodies. These tests have been rigorously tested and are designed to provide accurate results.

References:

• "Bleach Pregnancy Test: Science, Reliability, and More" - Healthline
• "Home pregnancy tests: Can you trust the results?" - Mayo Clinic