Twins never cease to be fascinating; the idea, especially in identical twin births, of two children being so much alike, never ceases to be intriguing.
A twin birth occurs when one sperm fertilises a single egg which then splits (identical), or when two eggs are independently fertilised by two different sperm cells during the same pregnancy (fraternal). Twin babies mean more work for mom -- she'll demand more of everything, from more folic acid to more doctors' visits, but parents of multiples will tell you that they are nevertheless double the joy.
Here are some interesting facts about twins:
*There are two types of twins -- identical and non-identical. Identical (monozygotic) twins occur when a single egg (zygote) is fertilised and then divides in two. These two children will share the same genes. Non-identical (dizygotic) twins occur when two separate eggs are fertilised by two separate sperm. These twins are like regular siblings.
* Because two separate eggs can be fertilised by two separate sperm, a woman can, in essence, carry two babies (twins) belonging to two different fathers -- termed Heteropaternal Superfecundation. Both men can fertilise his own egg from separate acts of sexual intercourse engaged in while the woman is ovulating.
* Identical twins are always the same sex.
* A woman might suspect that she's carrying twins if she is bigger than normal for her dates, or if she has had fertility treatment.
* Some identical twins have separate placentas. This occurs when the fertilised egg splits before being implanted in the uterus.
* No one knows what causes identical twins. The most accurate way of determining whether your twins are identical is through genetic testing.
* The older a woman is, the more likely she is to have twins, as changes in hormones means she can release more than one egg at a time.
* Sometimes what may seem like a normal twin pregnancy is later found to lead to only one baby. This is called vanishing twin syndrome, and no one knows
* Twins never cease to fascinate. There have been stories about them having their own language, and about one twin knowing what the other is feeling. A case in point, studied by Minneapolis psychologists in 1979, involved twin boys separated by adoption at three weeks and living miles apart. They found each other at age 39, and discovered that both had been christened James by their adoptive parents; as schoolboys, both enjoyed math and carpentry but hated spelling; both pursued careers in security; both married women named Linda, divorced and remarried women named Betty; and both had sons named James Alan Lewis.