18 Fun Facts About Twins

What you should know about these compelling carbon copies.

Twins | Loma Linda University Center for Fertility | California | photo of twins on a rocking horseNo your eyes are not playing tricks on you. If you think you are seeing double more often it is because you are. Pregnancies with twins and other multiple babies are on the rise.

The Centers for Disease Control and Prevention (CDC) reports that in 2015 there were 133,155 twin births in the United States, making up 3.35 percent of all births. This is down slightly from 2014 which had the all-time high twin births, making up 3.39 percent of all births. Between 1980 and 2009 the birth rate of twin rose 76 percent.

In 2012, the CDC looked into the cause for the rise and found that older women tend to have more twins than younger women. They discovered that women over 35 were having more babies, both naturally and with the help of infertility treatments, and that was the key contributor to the increase in twins.

Many people find twins fascinating, so I decided to gather some facts to help you brush up on your twosome trivia.

General facts about twins

  1. They speak their own language. Around 40 percent of twins make up their own languages. Usually the special lingo disappears as their vocabulary expands.
  2. Identical and fraternal aren’t the only kinds. Identical twins are the result of one egg splitting after fertilization, and fraternal twins are conceived with two eggs and two sperm at the same time. But those are not the only types of twins. Mirror-image twins occur when one twin is left-handed and the other is right-handed, and they will have birthmarks on opposite sides of their bodies.
  3. They are more likely to be left-handed. About 1 in 5 pairs are left-handed, or roughly double rate of the general population.
  4. One can absorb the other. It is estimated that 1 in 8 pregnancies start with twins but only 1 in 70 end up delivering two babies. This is because of vanishing twin syndrome where one of the babies doesn’t survive due to miscarriage and the other fetus absorbs its tissue. This usually happens early on in the pregnancy.
  5. Bonding starts in the belly. Researchers from the University of Padova in Italy studied 3D ultrasounds of five sets of twins in the womb. They found at just 14 weeks the pair seemed to be touching each other.

Identical twin facts

  1. Fingerprints are different in identical twins. Fingerprints are made as the babies move around and touch the amniotic sac, hence creating unique ridges and lines forming unique fingerprints that are not linked to the DNA.
  2. You can often tell identical twins apart by their belly button. Belly buttons are not caused by genetics. They are scars from the site of the umbilical cord, making them a way to distinguish between identical twins that might not have other unique identifiers.

Geography of twins

  1. New Jersey, America’s twosome capital. The CDC 2014 statistics show that New Jersey had the highest percent of twin births with 4.31 percent. However, the state with the most twin births in 2014 was California with 46,559 twins.
  2. New Mexico has the lowest twin birth rate. According to the 2014 CDC report, 2.4 percent of births in New Mexico were twins. The state with the least amount in 2014 was Vermont with 599 pairs.

Parents of twins

  1. Mothers of twins tend to live longer. The University of Utah completed a study that looked at the birth and death records between 1800 and 1970. It found that moms of twins tend to live longer than mothers of non-twins.
  2. Women who eat a lot of milk, cheese and yogurt are more likely to have two babies. According to a study completed in 2006, women who consume dairy products may raise the likeliness of conceiving twins. And non-vegans tend to have multiple babies 5 times more often than vegans.
  3. Taller women have a higher chance of twins. A study from 2006 found that on average mothers of twins or triplets were more than one inch taller than mothers with only one baby. The reason behind this is that insulin-like growth factor (IGF) is a protein released from the liver linked to height, as well as to ovulation.
  4. It’s possible that twins can have different dads. While it is rare, a woman can release two eggs during ovulation and get impregnated by two different men, one fertilizing one egg, and another partner fertilizing the other. This is known as heteropaternal superfecundation.
  5. Older moms are more likely to have twins. This is true even without in vitro fertilization (IVF).

Medical side of twins

  1. They can run in the family. A woman can inherit a gene that causes her to hyper-ovulate, meaning she is more likely to release multiple eggs while ovulating. These are fraternal twins because they each have a separate egg. But there is no known gene linked to having identical twins.
  2. They should be delivered at 37 weeks. This is done to reduce the chance of complications and stillbirth. If the babies share a placenta this move up to 36 weeks.
  3. You can deliver twins naturally. While C-sections are the most common delivery method with twins, vaginal births can be safe as well. If both heads are facing down and the babies and the placenta are in the right position, doctors likely try for a vaginal delivery. Women with twins also tend to go into labor earlier, not making it to full-term.
  4. The average time between delivering twins is 17 minutes. Usually after the first baby is delivered the second comes along quickly. Although that is not always the case, because at times there are hours between babies. This can also cause twins to be born on separate days.