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Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
According to research, pregnant women tend to eat more if carrying a baby boy. Male fetuses may secrete a chemical that stimulates their mothers to step up her energy intake.
After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
There are approximately 3 million unintended pregnancies in the United States each year.