1. Scientists believe that the number of twin conceptions greatly outnumbers the number of twin births. Twin conceptions are much more common than many people realize. Of course, these conceptions do not always result in the birth of two healthy babies. Very often, one of the fertilized eggs or embryos will be reabsorbed into the mother's womb in a phenomenon called "vanishing twin syndrome."
2. The incidence of twin types and genders are oddly symmetrical. These facts about twinning are sure to leave you in awe. One third of all twins born are identical, one third are same sex fraternal, and one third are male/female fraternal. Of the identical twins, half are male.male and half are female/female. Of the same sex fraternal, half are male/male, and half are female/female.
3. Twins do not have to be born on the same date. In fact, they can be born surprisingly far apart. The longest recorded gap between twin births is 85 days. How does this happen? The simplest explanation comes when one twin is born just before midnight and the other after. In cases where there is a longer gap, it's often because one twin is born early due to complications, while the other is left in the womb to further develop. This is much safer for the second baby and can help improve survival rates.
4. Identical twins have different fingerprints. Some people might think that identical twins are the same right down to those whorls and swirls on their fingerprints, but while identical twins share most of their genetic material, identical fingerprints aren't among them. While the fingerprints may be very similar, on close examination it is possible to tell them apart – much like the twins themselves.
5. About 25% of identical twins are called mirror image twins. This means that they are, in fact, identical, but only in the way that your reflection in a mirror is an identical image of you. For example, if one twin has a mole under her right eye, the other will have it under her left eye. Scientists think this is due to the fertilized egg splitting later than the norm for identical twins, around nine to twelve days after fertilization.
6. Twins often develop their own language. This phenomena is called idioglossia. It's something that has fascinated people about twins for years, but it's really a relatively simple and easily understandable process. It happens when one twin models the disordered or incorrect speech of the other, leading to both twins using the same grammatical or speech sound errors. It sounds like a foreign language, but is really just a normal part of cognitive development. 40% of twins invent their own language.
7. Twins share DNA, but it is not identical. While identical twins come from the same sperm and egg, their DNA isn't necessarily identical, according to new research. Scientists used to think differences in twins were due to environmental factors; they now know that isn't the only force causing variations. Genetic studies have demonstrated that there are certain points where twins will veer away from one another, with one carrying different or multiple copies of the same gene.
8. Certain diets may increase your chances of having twins. What a woman eats can help increase her chances of having twins, or so researchers think. While genetics obviously plays a big role, diet can also influence this phenomenon. Researchers have found that women who eat dairy and animal products are much more likely to have twins than those that don't. This is likely due to a protein called IGF that increases the sensitivity of the ovaries to hormones that cause ovulation.
9. Fraternal twinning is genetically predisposed. Identical twinning is random. Fraternal twinning is the result of a woman releasing multiple eggs at the same time, and is largely the result of a genetic predisposition to release this extras. Identical twins, however, are the result of a random split of a single egg, something which cannot be genetically predisposed. In recent years, the number of fraternal twins has risen in response to fertility treatments, while the number of identical twin births has stayed the same.
10. 27 lbs and 12oz is the heaviest combined birth weight of any set of twins. if you think it would be rough to carry around and deliver one 14-pound baby, then imagine doing it with two. That's just what happened in this case, the largest twin birth on record. Of course, it doesn't hold a candle to the largest singleton birth weight of 23 pounds.
11. Turns out there are ways to up the chances you'll deliver two bouncing babies. Being tall is one of them. Past research has found that taller women have more of an insulin-like growth factor that has been linked to both height and the rate of twins.Those who birthed two or more children were on average more than an inch taller than other mothers, according to the study published in September 2006 in the Journal of Reproductive Medicine. As a woman ages, she's also more likely than her younger counterparts to have multiple births.
12. Birth rate statistics for identical twinning have remained stable over the years, despite the overall increase in twins and multiples since the late 1980's. The odds of having identical twins is about 3 in 1,000, whereas the birthrate for all twins is about 32.2 in 1,000.
13. Over 50% of twins are born before 37 weeks.The average birth weight for a twin is 5lbs, 5 oz.