Scientific Method in Action:  Semmelweis and “Childbed Fever”

During the 1840s the incidence of “childbed fever” differed in the two maternity wards at Vienna General Hospital
• Ward 1 (lower socioeconomic level) death rate = 11.4%
• Ward 2 (higher socioeconomic level) death rate = 2%

His Observations:  
1. Ward 1 more crowded
2. Women of Ward 1 birth position on back, Ward 2 on side
3. Priests walked through Ward 1 after giving last rites to dying patients in other wards
4. More student doctors on Ward 1

His Hypotheses:
1. Overcrowding causes higher mortality rates in Ward 1
2. Birth position causes higher mortality rates in Ward 1
3. Priest’s presence upsets women weakened by childbirth, causes higher mortality rates in Ward 1
4. Student doctor’s techniques, rougher than experienced doctor’s, cause higher mortality rates in Ward 1

Test hypotheses / Collect data:
1. Overcrowding causes higher mortality rates
    •Test predictions: If reduce crowding, mortality will decrease
    • Experiment: Reduce crowding
    • Data collection: No reduction in mortality

2. Birth position causes higher mortality rates
    •Test predictions: If change position, mortality will decrease
    • Experiment: Change birth position from back to side
    • Data collection: No reduction in mortality

3. Priest’s presence causes higher mortality rates
    •Test predictions: If no priest, mortality will decrease
    • Experiment: Change route of priests
    • Data collection: No reduction in mortality

4. Student doctor’s techniques cause higher mortality rates
    •Test predictions: If techniques improve, mortality will decrease
    • Experiment: Teach student doctors better techniques
    • Data collection: No reduction in mortality

Use data to evaluate hypotheses:
1. Overcrowding causes higher mortality rates
    • Data collection: No reduction in mortality
    • Hypothesis rejected as false
 
2. Birth position causes higher mortality rates
    • Data collection: No reduction in mortality
    • Hypothesis rejected as false
 
3. Priest’s presence causes higher mortality rates
    • Data collection: No reduction in mortality
    • Hypothesis rejected as false
 
4. Student doctor’s techniques cause higher mortality rates
     • Data collection: No reduction in mortality
     • Hypothesis rejected as false 

Revise hypotheses if necessary:
> Then something unexpected happened: A fellow physician who accidentally cut himself during an autopsy died with the same symptoms as the women with childbed fever

He made new observations:
  > Student doctors frequently performed autopsies, and then went to deliver babies without washing their hands (bacteria and viruses were unknown in the 1840s).  Perhaps they were transferring something from the cadavers to the women that caused women to become ill and die.

    • New hypothesis: Student doctor’s dirty hands cause higher mortality rates
    •Test predictions: If hands are washed, mortality will decrease
    • Experiment: Teach student doctors to wash hands carefully
    • Data collection: Reduction in mortality
    • Hypothesis not falsified