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Chapter 10
Double Delight: Twins
(Brief excerpt of book chapter)
Approximately one pregnant woman out of 90 in the United States gives birth to twins. There are two types of twins -- fraternal and identical:
Fraternal twins are separate right from the beginning, occurring when two eggs are released by the ovary and each is fertilized by a different sperm. So despite the fact that fraternal twins share space inside the uterus, they are no more alike than any other pair of siblings that come from the same parents. (One can be a boy and one a girl, for example.)
Identical twins arise from a single sperm-egg pair. Within a few days after fertilization the group of dividing cells splits into two parts--each with the same genetic makeup, which will result in two identical babies.
Watching twins grow:
| Six-week identical twins | |
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| Nine-week identical twins | |
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| Sixteen-week twins. We can’t tell whether these are identical or fraternal. | |