Pregnancy tests haven’t always been as readily available & reliable as they are today. Before the outbreak of the Second World War, scientists discovered a new improved method, involving the African Clawed Frog.
Xenopus laevis is a common species of frog found throughout much of Sub-Saharan Africa. These early pregnancy tests involved injecting the female frogs with the urine of a suspected pregnant women. When the scientists returned to the frog in the morning they looked out for frog eggs in the water. If the frog had ovulated the woman is pregnant. If this didn’t happen the result was negative.
Why does this work? The answer is that pregnant women produce key hormones in much higher concentrations. The human hormone gonadotropin can also cause a female frog to ovulate.
Although frogs aren’t used in pregnancy tests today, we still use the lessons learned from this practice. Xenopus laevis are commonly used in labs around the world as a model organism in developmental biology. This requires embryos all year round. Scientists today still inject frogs with gonadotropin, just it’s artificially sourced, meaning you don’t need to collect urine samples anymore! This allows for frogs to be bred in the lab throughout the year, not just in the mating season