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Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
Only 12 hours after an egg cell is fertilized by a sperm cell, the egg cell starts to divide. As it continues to divide, it moves along the fallopian tube toward the uterus at about 1 inch per day.
Asthma is the most common chronic childhood disease in the world. Most children who develop asthma have symptoms before they are 5 years old.
Each year in the United States, there are approximately six million pregnancies. This means that at any one time, about 4% of women in the United States are pregnant.
After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.