Two in the time of one
It is the dream of many a woman to give birth to twins. Twins are such a rare occurrence that they bestow instant celebrity status on the parents in general and the mother in particular. The new spreads wide and the occurrence of twins is any way a dissonance in the respect that normally the births are single child births. In many cultures twins being born are not looked in a scientific way but women who give birth to twins become myth. However in recent years medical science has begun to understand the science behind this biological event.
The science behind the joy
There are two types of twins namely fraternal and identical. Fraternal twins are produced from two different eggs that are each fertilized by different sperm, which results in two embryos with different genetic make-up. On the other hand when a fertilized egg divides into two and each ‘halve’ having the same genetic make-up grows into a baby, the two babies are called identical twins. The propensity to bear fraternal twins runs in some families, but not in every generation sequentially. The probability of fraternal twins occurring is about 12 in every 1000 births. Right now there is no evidence to suggest that having identical twins is affected by genetics. Identical twins occur in approximately 4 out of every 1000 births. The likelihood of having identical twins is no more common in any one group of people. Fraternal twins happen when a gene which makes fraternal twins more likely is inherited. This gene is present on the X chromosome and may cause hyper ovulation. Hyper ovulation is when a woman’s ovaries release more than one egg per ovulation cycle. The woman can inherit this gene from any of her parents. A man with a family history of twins is not likely to father twins himself. However if a man has fraternal twins in his family, he might pass on the twin gene to a daughter.
The probability of fraternal twins is impacted whether a particular generation has more males or females. If a family has more daughters than sons the chances of having twins would automatically go up.
It’s not luck
There are other factors which appear to influence the probability of a woman releasing more than one egg per cycle. Woman of African descent are twice as likely that their Caucasian counterparts to have twins. Well nourished, health women between the ages of 20 and 35 are also likely to have twins as compared to women of lesser health. Science does not fully understand this phenomena but having twins or not is definitely not luck.
