Twins Babies facts

• On average, twins are born 22 days premature.
   
• On average, twins are born 5 lb 5 oz., average weight of singleton babies is 7 lb 7 oz..
   
• One set of twins is born to each 100 couples each year in the US. The statistics has doubled in the past couple of decades.
   
• Other statistics say that there is one set of twins per 90 child births. The statistics is highest in African American and lowest in Asian population. Someone told me it is about one in 300 for Asian twins. The statistics for identical twins is even lower.
   
• Due to advances in ultrasound imaging technology, the medical world discovered only recently that twin conception is more common than we knew. At least one-eighth of all natural pregnancies begin as twins. Perhaps due to the genetic making of the mother, most twins are not carried through the entire term. One of the twin embryos is rejected by the mother's body and is absorbed back into the mother's tissue within the first few weeks of conception. This is known as the "disappearing twin" or "vanishing twin" .  In some cases, the evidence of the second baby is discovered before it is totally absorbed, but in most cases, the second twin had already disappeared by the time the mother took her pregnancy test. That's why this phenomenon is not known until recently. Perhaps better prenatal care helps the second twin to survive the first few weeks, hence more twins are born nowadays.
   
• Most people know there are two types of twins, namely fraternal twins and identical twins. However, among the identical twins, there are some that are not so identical. They are mirror twins. They are mirror image of their twin sibling. For example, one is right handed and the other is left handed. Some external features such as hair, moles etc. are on the opposite side. Some even have their internal organs grow on the opposite side.

  It is hard to believe, but one in every 8,500 people on earth have a medical condition called situs inversus. Researchers believe that the condition is closely related to primary ciliary dyskinesia. For most people, the heart rests on the left, the tri-lobed lung is on the right, the bi-lobed lung is on the left, the stomach and spleen fill the left side of the abdominal cavity, the liver and gall bladder the right, and the intestines run from right to left. These people with situs inversus have the normal left-right placement of their organ flip-flopped. Not all mirror twins are situs reversus, or situs reversus always have a twin sibling. However, it is puzzling to science that two individuals with identical DNA can grow up to be opposite of each other.