Did you know that the number of twin births have more than doubled since the early 1970s? Today, about one of every 35 births in the United States are twins. Even more significant is the number of triplet and higher multiple births which have increased 200 percent over the last three decades.

Why the huge jump in the number of multiple births?

The most obvious reason for the growing birth rates of twins and multiples is the use of fertility drugs and treatments. These medical interventions are most often the reason for births of four or more multiples. Recent studies from the Center for Disease Control (CDC) show that approximately 43 percent of live births resulting from assisted reproductive techniques were multiples.

But fertility drugs dont tell the whole story.

Where you live could make a difference. If you reside in Massachusetts or Connecticut, a study by the National Center for Health Statistics found that the rates for twin deliveries was as much as 25 percent higher than the overall national rate. If you want to give birth to triplets, move to Nebraska or New Jersey. Both states boast a percentage of triplets that is twice the national average.

On the other hand, if you reside in tropical Hawaii your chances of having a multiple will decrease to about 30 percent below the overall U.S. rate.

The time of year and the number of daylight hours also has an impact on multiple births. More fraternal twins are conceived in July than in any other month, while January has the fewest twin conceptions. Scientists speculate that this is probably due to the longer length of daylight in July, which allows for a higher secretion of the Follicle Stimulating Hormone in women.

Enhanced medical care and good nutrition may play a role in skyrocketing multiple birth rates, although experts caution that it is difficult to directly link these influences. In fact, if access to state-of-the-art medicine were a deciding factor, then why does the Yoruba tribe of Nigeria have the highest twinning incidence in the entire world? These Nigerian people attribute it to their populations consumption of a specific type of yam. Yams? Thats right, scientists have discovered that these colorful vegetables that are grown only in Africa contain a high level of a substance that is similar to the hormone estrogen -- which could bring on multiple ovulation.

Surprisingly, age can work in a womans favor when it comes to conceiving twins. Older mothers traditionally have a higher chance of delivering fraternal twins, with the odds increasing to one in 27 when the mother is 35 years or older.

While identical twins have no familial connection, it is true that fraternal twins can run in the family. Female fraternal twins score an impressive one in 17 chance of giving birth to their own set of fraternal twins, probably because many carry a gene for hyperovulation, which means they sometimes release more than one egg during ovulation. And, if a woman has already given birth to fraternal twins, the chance of another set increases fourfold.

Want to learn more about babies and multiples? Visit the All About Baby website at http://www.allbaby.com for extensive child-related content, including tips on how to pick the best name for your newborn, interesting birth statistics, a list of the most popular given names for children and much more.

**All statistics were taken from the Center for Disease Control (CDC), the National Center for Health Statistics and from the National Organization of Mothers of Twins Club (NOMOTC).