A baby begins as a fertilized egg – a pinhead-sized egg cell from the mother, which has joined an even smaller tadpole-shaped sperm cell from the father. Although thousands of these sperm cells may cluster around the egg cell, only one of these will actually fertilize the egg.
Non-identical twins are produced when two eggs are released at the same time, and both are fertilized. They can be the same sex, or brother and sister.
Identical twins are produced when the embryo splits into two in the early stages of its development. This produces two identical children of the same sex. Some identical twins look so alike that they can only be told apart by their fingerprints.
Only one in 83 pregnancies results in twins.
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Fact File: The bones of a baby’s head are not fully fused at birth, allowing the skull to pass through the mother’s birth canal. The bones gradually become joined, but a gap at the top of the skull, called the fontanelle, may not close up for several months. |
Picture Credit : Google