FRATERNAL TWINS : Your Bundle(s) of joy

If producing babies is no mean feat, then what about producing them two-at-a-time?
Nowadays, about 1 in every 90 births turn out to be twins and there is almost a 75% chance that the twins would be fraternal sets (or more commonly - non identical twins). Over the past 2 decades, the number of fraternal twins has increased dramatically and after much observation and experimentation, our scientists have outlined the major reasons behind this unexpected rise in number:-

Superfoetation
This is an interesting case where the mother releases an egg and becomes pregnant, but after a few days (sometimes up to 24 days) she would release another egg which would also get fertilized. Obviously, the sperms fertilizing these two eggs are different and can belong to separate men. These fertilized eggs now implant themselves in the uterus of the mother either on opposite sides, or close to each other. If the eggs are too close, then their amniotic membranes (protective membranes around the developing embryo) and their placantae may fuse, thereby fooling the doctors to declare them to be 'identical twins' when they are very much a fraternal set.
Superfoetation can also occur in the case of a woman undergoing Invitro Fertilization (IVF). Here, the egg from the donor is aspirated out of her body, fertilized and then artificially implanted in the uterus of the mother; around the same time, the mother might release another egg (during her regular cycle) which if fertilized by natural means would give rise to fraternal twins.
Though both the twin babies have different dates of conception, they are delivered on the same day. Therefore, one of the twins is actually slightly premature!

Superfecundation
This condition is purely genetic, where a woman releases more than one egg during her regular cycles (superovulation/hyperovulation). Thus, when such a woman becomes pregnant, both her eggs would have been fertilized by different sperms resulting in fraternal twins.
If you have mothered fraternal twin babies, a common question that many people would have asked you is : "Do twins run in your family?" This is because, the case of Superfecundation bears testimony to the popular saying: "Twins are hereditary".
But today, many aspiring mothers turn to fertility drugs which also cause them to superovulate and bear non-identical twins.

Fraternal twins are like normal siblings - neither do they look similar nor do they share the same genes. In fact, they show a 50% variation in their DNA (unlike an identical set). It has been proven that fraternal twins share an intimate relationship and can be closer to each other than identical twins! Perhaps the reason is that the former pair does not have to strive to discover their own identity and uniqueness. Each fraternal twin also has the advantage of having a constant companion of his own age with whom he could share his experiences and discuss his problems.
President Bush's twin girls and (closer home) E.F. Minister Shashi Tharoor's twin sons are perfect examples of fraternal sets.

These twins develop a strong friendship that is often unbreakable and long-lasting.
After all, they began their journey together... didn't they?