If you’ve recently discovered you’re expecting or are in the process of trying to conceive, you probably have a lot of questions. If twins run in your family, one of those questions might be about the different kinds of twins. Or perhaps you’re already aware you’re having twins but haven’t had the opportunity for further testing yet. Regardless, you’re here to explore the various types of twins that can occur during pregnancy — and we’re excited to share this knowledge with you.
You may have previously thought that twins fell into just two categories: identical and fraternal. However, there are actually several more types! Plus, there are some rare twin-specific events that can happen during pregnancy, leading to even more unique “types.” Get ready to become an expert on all things twin-related.
How Common Are Twins?
You probably know at least one set of twins, even if just by acquaintance. The reality is that twins are more prevalent today than you might realize. According to the Centers for Disease Control and Prevention (CDC), the rate of twin births has surged by approximately 78 percent since 1980. Currently, about 34 out of every 1,000 births in the United States are twins. This increase aligns with advancements in fertility treatments over the years.
What Are the Primary Types of Twins?
If someone were to casually ask you what types of twins exist, you’d likely mention fraternal and identical, and you’d mostly be correct — these two categories encompass the majority of twin births. While there are some unusual variants and occurrences, let’s focus on these two for now.
Fraternal (Dizygotic) Twins
Fraternal twins are the most common type, developing when two separate sperm cells fertilize two separate eggs, often as a result of the mother releasing two eggs during ovulation. Each fertilized egg implants in the uterus and grows. Fraternal twins share about 50 percent of their DNA, making them genetically similar to non-twin siblings. They can be two girls, two boys, or one of each. While they may resemble each other like many siblings do, they are not identical.
Identical (Monozygotic) Twins
Identical twins, or monozygotic twins, form when a single fertilized egg splits into two embryos. Depending on when the split occurs, they may share the same placenta or amniotic sac. As their name suggests, these twins are genetically identical, sharing the same DNA and genetic traits such as blood type and eye color. However, they might not look exactly alike due to environmental factors. Identical twins start with identical DNA, but individual characteristics can emerge over time, making each twin a unique individual.
How Can You Determine If Your Twins Are Identical or Fraternal?
It can be challenging to tell if twins are identical or fraternal, especially since identical twins may not always look alike. If you’re pregnant and curious about the type of twins you have, the only definitive method is through a DNA zygosity test, which compares the DNA profiles of each twin.
Are There Other, More Uncommon Types of Twins?
Yes! Some types you might be familiar with, while others may be new to you. They include:
Mirror Image Twins
This type of identical twins occurs when the fertilized egg splits more than a week after conception. The result is that the twins develop with asymmetric features that appear to be mirror images of each other, like differing birthmarks or cowlicks going in opposite directions.
Semi-Identical Twins
In this rare occurrence, two sperm fertilize one egg, leading to three sets of chromosomes. The egg then splits, resulting in two fetuses. Semi-identical twins are extremely uncommon, with only two documented cases.
Polar Body or “Half-Identical” Twins
This theoretical type occurs when an egg splits and each half is fertilized by a separate sperm. While these twins would share more genetic material than fraternal twins, there is no definitive test to confirm their existence.
Superfetation
This rare phenomenon allows for twins to be conceived at different times. It happens when a fertilized egg is implanted, and then a woman’s cycle resumes, leading to the release and fertilization of another egg.
Heteropaternal Superfecundation
Also known as “bi-paternal” twins, this occurs when eggs are fertilized by sperm from different instances of sexual intercourse, resulting in twins with different fathers.
What Types of Twins Are Caused by Pregnancy Events?
In rare cases, twins arise from complications during pregnancy. These include:
Conjoined Twins
A type of identical twins formed from the incomplete division of a fertilized egg, resulting in the twins being physically joined at certain body points.
Parasitic Twins
A subset of conjoined twins where one fetus fails to develop fully and relies on the larger twin. This can manifest as a fetus in fetu or an acardiac twin.
Chimerism
When one embryo absorbs the cells of its deceased twin, the surviving twin may possess two sets of cells, resulting in a chimera.
Does Carrying Twins Result in More Pain?
Surprisingly, carrying twins isn’t necessarily more painful than carrying one baby. Each woman’s experience varies, but most mothers report discomfort during pregnancy rather than during delivery. Common complaints include back pain, sleep disruption, and intense heartburn. However, mothers expecting twins do face higher risks such as maternal anemia and gestational hypertension. Thus, while having twins doesn’t automatically mean a more painful pregnancy or delivery, it does come with distinct challenges.
Are There Tips for Increasing Your Chances of Having Twins?
If you and your partner are hoping to welcome twins, there are a few traditional tips you might consider. Consuming dairy products, sweet potatoes, and cassava may increase the likelihood of releasing more than one egg. Nigeria, known for the highest twin birth rate in the world, often attributes this phenomenon to the consumption of cassava.
For more information on pregnancy and home insemination, check out this excellent resource about intrauterine insemination. If you’re interested in learning more about fertility assessment packages, visit this authority on the topic.
Summary
Understanding the different types of twins can be fascinating, with many more variations than just identical and fraternal. From mirror image twins to semi-identical twins and even chimerism, the world of twin pregnancies is full of surprises. While carrying twins can come with its own set of challenges, it’s not necessarily more painful than carrying a single child. If you’re curious about increasing your chances of having twins, consider exploring some traditional suggestions.
Keyphrase: Types of Twins