Parents can pass along all sorts of attributes and personality traits to their kids, like eye and hair color, cute little dimples, and quirks and kinks that they can blame them for later in therapy. It's all part of the science behind genes and other things regarding DNA that I won't pretend to fully understand. But what about when you exit the womb with a partner in crime? We know all about the unbreakable bond between twins, but what exactly are the ins and outs of creating a duo? Do twins skip a generation?
"According to conventional wisdom, twins not only run in families, but they also — for some strange reason — always skip at least one generation," The New York Times noted. "It is a claim that is widely repeated, but only partly true." The newspaper said the notion may stem from the fact that men who inherit the gene from their mamas can't do anything with it because, ahem, they don't ovulate. But they can still pass it along to their daughters. Even still, while twins can indeed run in families, they do not necessarily skip a generation, the NYT said.
According to the Centers for Disease Control and Prevention (CDC), the 2016 twin birth rate was 33.4 twins per 1,000 births, an ever so slightly lower rate than that in 2015 of 33.5. The 2014 rate of 33.9 was the highest ever reported, the CDC noted.
Of course, if you are someone who wants to have twins, then you may be wondering if you can increase your chances of having them. "The answer is, yes, you can increase your chances of having twins, but this is a matter of statistics and not by any means a guarantee," says Dr. Steven Hausman, president of Hausman Technology Presentations and a former research scientist at the National Institutes of Health, in an email interview with Romper. "The likelihood of conceiving twins is not determined by any single trait. Rather, it is a complex process that probably involves multiple genetic and environmental factors, depending on the type of twins."
In case you didn't know, there are two types of twins: monozygotic (MZ) and dizygotic (DZ). In short, MZ twins — or identical twins — occur when a single egg cell is fertilized by a single sperm cell and the resulting zygote splits in two. Identical twins are most often not caused by genetic factors, except for in the rare case where a family has multiple sets of identical twins, Hausman says.
On the other hand, DZ twins — also known as fraternal twins — occur when two egg cells are each fertilized by a different sperm cell in the same menstrual cycle, says Hausman. Fraternal twins are about twice as common as identical twins, and they are much more likely to run in families.
Factors that influence the likelihood of fraternal twins include maternal age, race, and even being a twin yourself. More controllable factors include nutritional tips, like eating wild yams (cassava root) and dairy products — although Hausman points out this could be the result of cows being treated with growth hormones. Folic acid for women and zinc for men has also been shown to boost chances of a multiples pregnancy, and breastfeeding while trying to become pregnant can also help. Fertility drugs and in-vitro fertilization will improve the odds too, according to WebMD.
Like anything related to pregnancy and birth, it sounds like a lot of these twins shenanigans are up in the air. Because if there's anything the time of carrying your child (or children) can prepare you for it's this: Be prepared to have your plans changed. In short, you're going to learn how to be flexible in order to handle whatever comes your way, including that dual bundle of joy.
Check out Romper's new video series, Bearing The Motherload, where disagreeing parents from different sides of an issue sit down with a mediator and talk about how to support (and not judge) each other’s parenting perspectives. New episodes air Mondays on Facebook.