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About 3% of all pregnant women will give birth to twins, which is an increase in rate of nearly 60% since the early 1980s.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
Symptoms of kidney problems include a loss of appetite, back pain (which may be sudden and intense), chills, abdominal pain, fluid retention, nausea, the urge to urinate, vomiting, and fever.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
For about 100 years, scientists thought that peptic ulcers were caused by stress, spicy food, and alcohol. Later, researchers added stomach acid to the list of causes and began treating ulcers with antacids. Now it is known that peptic ulcers are predominantly caused by Helicobacter pylori, a spiral-shaped bacterium that normally exist in the stomach.