What is the control group in Ignaz Semmelweis's hypothesis?

In Ignaz Semmelweis's hypothesis, the control group refers to the group of patients treated by doctors and medical students who did not wash their hands before delivering babies. This group experienced higher rates of puerperal fever compared to the experimental group, which involved midwives who practiced hand hygiene. Semmelweis used this comparison to demonstrate the importance of handwashing in reducing infection rates. The control group thus served as a baseline to highlight the effects of hygiene practices on patient outcomes.