Pregnancy tests have not always been as readily available as they are today.
Just before the outbreak of the Second World War, scientists developed a new & improved method, involving frogs. Early pregnancy tests involved injecting female frogs with human urine from a potentially pregnant woman. When scientists returned to the frog in the morning, they would check for frogspawn – an accumulation of frog eggs
Why does this pregnancy test work?:
- Pregnant humans have elevated concentrations of hormones known as gonadotropin – which includes FSH and LH
- Gonadotropin will be present in human urine of pregnant women
- Gonadotropin causes frogs to ovulate, as the hormones used during ovulation are similar for most vertebrates
- If urine from a pregnant woman is injected into a female frog, the frog will ovulate
- So, if frogspawn is found after injecting urine, the human is pregnant
- But if there is no frogspawn, it is likely the woman is not pregnant
Although advancements in pregnancy testing technology has made this technique redundant, the lessons learned from this practise are still used today in research science. Developmental biologists use Xenopus laevis, the African Clawed Frog, extensively as a model organism for embryo development. They can inject gonadotropin to collect frog eggs for research. Thankfully, gonadotropin can be artificially sourced, meaning human urine is no longer needed! The constant supply of eggs for developmental studies has accelerated the rate of key discoveries.