Today’s expert is author and twin mom, Susan Heim!

Twins and multiples have fascinated people for thousands of years! In fact, a lot of things are still unknown about them, so I thought I’d answer a few of the questions that people often ask about multiples:

Can Identical Twins Be NOT Identical?

Even though identical twins share the same genes, they can be very different in many ways. Sometimes they are different sizes, have differing likes and dislikes or exhibit separate personalities. This occurs because human development is not strictly determined by our genes. For instance, if twins share a placenta and one has a “better connection” to the nutrients it provides, this twin may be bigger or display other differences. Scientists also speculate that natural chemical changes in our genetic material may affect the way certain genes dominate. This may explain why identical twins tend to show more differences as they get older and don’t spend as much time together—their natural chemical changes affect their development as individuals.

Which Women Are Most Likely to Conceive Twins?

First, women of “advanced maternal age” (as my doctor labeled me unflatteringly) are more likely to conceive twins. As they get closer to menopause (after age thirty-five), they begin to ovulate more irregularly. Therefore, the chances of releasing more than one egg in a given menstrual cycle are higher. For some reason, as well, if women already have children, they’re more likely to have twins. In fact, the probability of having twins is three times higher in women over the age of thirty-five with at least four other children than for women under twenty who are pregnant for the first time. In addition, African-American women have a 1 in 79 chance of conceiving twins; Caucasian women have 1 chance out of a hundred; and Asian women conceive twins more rarely—1 in 155 pregnancies. Finally, when women first stop taking the birth-control pill, their pituitary glands kick in with higher amounts of stimulation than usual, so the chance of conceiving twins is greater in the first month off the pill.

Do Twins Have a Special Language?

Just like married couples, your twins spend so much time together that they may develop particular “code words” that they use to communicate. For instance, if one calls his blanket a “bubby,” the other may soon follow suit. But this tendency, called “idioglossia” or “cryptophasia,” can’t be classified as a separate language. Just like singletons, when twins first start talking, they have trouble pronouncing certain words. As they pick up each other’s habits of saying things, they develop their own “secret code.” But as their speaking skills improve, the “twin language” will disappear.

Are More Twins Born During a Particular Season?

Surprisingly, the answer is yes! In areas that experience long summer days, such as the northern parts of Japan and Finland, more fraternal twins are conceived in the month of July. It’s theorized that the weather causes increased levels of the follicle stimulating hormone (FSH) in women, which affects the number of eggs that are released each month. So, if you want to conceive twins, try scheduling your next vacation in northern Japan in July!

Do Identical Twins Have the Same Fingerprints?

You might be surprised to learn that identical twins are not identical in every way. It’s not clear why, but they have different fingerprints! This often comes in handy when parents take their identical twins home from the hospital and remove their hospital bracelets. If they can’t tell the twins apart, they can be fingerprinted again and matched with the prints taken at the hospital.

Do Twins Skip a Generation?

There is no scientific proof that giving birth to twins skips a generation. Of course, it sometimes happens, but twins can just as easily be conceived in every generation of a family, or once and never again! However, women in a particular family can have a genetic predisposition for producing more than one egg during a menstrual cycle, therefore making them more likely to have twins. This is why it sometimes seems that “twins run in the family.” Note that since these twins are the result of multiple eggs being fertilized, this “genetic component” only holds true for fraternal twins.

Is There Always a “Good Twin” and a “Bad Twin”?

Of course not! Like any two siblings, twins are going to have differences in personality or go through different developmental stages. One may go through a stage where he’s sweet as molasses, while the other one makes you want to tear your hair out! But beware, just as you’ve slapped the “good” or “bad” labels on your twins, they’re likely to go through a new stage in which they’ll swap roles. All children have challenging periods of development. Unfortunately (or is it fortunately?), twins usually pick different times to do so.

What Are Mirror-Image Twins?

Mirror-image twins are identical twins that result from the splitting of the fertilized egg late in the embryonic stage. About twenty-five percent of identical twins are classified as “mirror-image,” and of the 6.3 billion people in the world, only 5 million are mirror-image twins. How do you know if you’re looking at mirror-image twins? If you have them face each other, certain traits will match up as if one was looking into a mirror. For example, their cowlicks may match (one on the left side of the head; one on the right side), or one may be left-handed and the other right-handed.

Susan is the author of “It’s Twins” and “Chicken Soup for the Soul: Twins and More”. Click on the books for more info.

You can visit Susan’s parenting blog here! Be sure to stop by and say hello!