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The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Approximately 70% of expectant mothers report experiencing some symptoms of morning sickness during the first trimester of pregnancy.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
Human stomach acid is strong enough to dissolve small pieces of metal such as razor blades or staples.
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