Table of ContentsView AllTable of ContentsTypes of TwinsRole of Twin Genes in Family HistoryBenefits of Identical Twin StudiesTesting, Growth, and BirthParenting Identical TwinsFrequently Asked Questions
Table of ContentsView All
View All
Table of Contents
Types of Twins
Role of Twin Genes in Family History
Benefits of Identical Twin Studies
Testing, Growth, and Birth
Parenting Identical Twins
Frequently Asked Questions
While they may look alike, identical twins are unique individuals with their own personalities and interests.
Identical twins, also known asmonozygotictwins, share the same egg atconceptionand are always either both boys or both girls.Fraternal twins, also known asdizygotictwins, come from two separate eggs fertilized at the same time. They could be the same sex or different.
Factors that increase the chances of having twins include the use of fertility drugs or treatments, a maternal age of over 30 years old, and a family history of twins or multiples. Twins and multiple pregnancy babies are at increased risk of being born prematurely and with low birth weight.
This article will discuss common misconceptions about identical twins. It will also describe their similarities and differences, as well as tips for parenting twins.
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What You Need to Know About a Twin Pregnancy
The two types of twins are identical and fraternal. They differ in the way they are conceived and their genetic makeup.
Fraternal vs. Identical
Identical twins share 100% of their genes. They are always born of the same sex.It can be challenging to tell identical twins apart. Whereas fraternal twins often look more like siblings than twins. They share 50% of their genes and could be of the same or different sexes at birth.
What Are Mono Mono Twins?
Conception
The differences between identical and fraternal twins are due to how they are conceived. When identical twins are conceived, the fertilized egg splits into two, causing two separate embryos to grow. When fraternal twins are conceived, two eggs are fertilized at the same time.
Factors that increase your chances of having twins include:
Everything You Need to Know About Conjoined Twins
Third Twin Theory
There is a theory that there is a third type of twin in between identical and fraternal. Semi-identical twins are a rare type of twins who share 100% of the genes from their mother but only 50% to 75% of the genes from their father. How is this possible? Well, the theory is that when two separate sperm fertilize the same egg and the egg splits into two embryos, you get semi-identical twins.
What Are Genes, DNA, and Chromosomes?
Fraternal twins, on the other hand, may run in families. Fraternal twins make up about 6% to 8% of live births in the United States.A woman who has a mother or sister who had fraternal twins is twice as likely to have them herself.
Fraternal twins happen when a woman releases multiple eggs (instead of one) during themenstrual cycle, which is known as hyperovulation, and may run in families. Factors that increase your risk of hyperovulation include:
Identical twins are incredibly helpful to researchers when they choose to participate in twin studies. Health researchers often examine the influence of both our genetic makeups and our environments to understand the causes of health conditions. This is often referred to as “nature or nurture.”
Identical Twin StatisticsThe identical twin birth rate in the United States is 32.1 per 1,000 live births. In 2019, about 120,291 sets of twins were born.
Identical Twin Statistics
The identical twin birth rate in the United States is 32.1 per 1,000 live births. In 2019, about 120,291 sets of twins were born.
The first prenatal test to consider is diagnosing a twin pregnancy. Research suggests that up to 40% of twin pregnancies are not diagnosed until the 13th week of pregnancy.Anultrasoundcan determine if twin babies are identical or fraternal.
Twin pregnancies are also more likely to end in preterm delivery.Preterm delivery occurs before 37 weeks gestation. Full gestation is 40 weeks. One of the reasons why twins are more likely to be born early is because the usual medical interventions that prevent preterm labor in singleton pregnancies are not effective for twin pregnancies. Because twins are more likely to be born early, they are also more likely to be considered low-birth-weight.
Labor and delivery are different and more complicated for twin pregnancies as well. For a twin pregnancy, the mother is usually taken to the operating room instead of a standard delivery room. This is because twin pregnancies are more likely to requirecesarean section(C-section) surgery. However, it is possible for mothers of twins to deliver vaginally.Talk with your healthcare provider about how to prepare.
Week-to-Week Pregnancy Timeline
Parenting identical twins comes with its own special challenges and rewards. It is helpful to prepare for twins’ unique parenting needs before they arrive and as they grow.
Special considerations when raising twins:
How parents and caregivers can support their twins:
Parenting twins can be both incredibly rewarding and exhausting. It is important to keep your own needs in mind, such as:
How to Tell Your Twins ApartEven parents can have a difficult time telling their identical twins apart. To tell newborn twins apart, try color-coding their clothing or using name bracelets. As they age, their unique personalities will tell them apart.
How to Tell Your Twins Apart
Even parents can have a difficult time telling their identical twins apart. To tell newborn twins apart, try color-coding their clothing or using name bracelets. As they age, their unique personalities will tell them apart.
Summary
Identical twins have fascinated researchers and parents for decades. When they are conceived, a single fertilized egg splits into two embryos. While identical twins look alike, their personalities, interests, and needs can be very different.
A Word From Verywell
If you are a parent to twins, you know how much joy they can bring to your life. It’s also helpful to name the unique challenges so that you can seek out the support you need. When your twins are babies, ask for help with childcare, cooking meals, house cleaning, and other tasks.
Frequently Asked QuestionsIdentical twins have unique ways of communicating with one another. While they cannot actually read each other’s minds, they learn each other’s facial expressions and gestures because they spend so much time together. This gives them unique insight into each other.Identical twins make up about 3% of live births in the United States.Fraternal twins tend to run in families. This may be due to hyperovulation, releasing more than one egg during the menstrual cycle, which is genetic. Because the mother is the one who ovulates, she is the one who is responsible for the increased chance of twins.Identical twins can be especially difficult to tell apart as newborns, even for their parents. If you are concerned about telling your babies apart, consider color-coding their clothing or having them wear bracelets with their names on them. As they age, their unique personalities will help to distinguish them from one another.
Identical twins have unique ways of communicating with one another. While they cannot actually read each other’s minds, they learn each other’s facial expressions and gestures because they spend so much time together. This gives them unique insight into each other.
Identical twins make up about 3% of live births in the United States.
Fraternal twins tend to run in families. This may be due to hyperovulation, releasing more than one egg during the menstrual cycle, which is genetic. Because the mother is the one who ovulates, she is the one who is responsible for the increased chance of twins.
Identical twins can be especially difficult to tell apart as newborns, even for their parents. If you are concerned about telling your babies apart, consider color-coding their clothing or having them wear bracelets with their names on them. As they age, their unique personalities will help to distinguish them from one another.
13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
MedlinePlus.Twins, triplets, multiple births.
National Human Genome Research Institute.Identical twins.
National Human Genome Research Institute.Fraternal twins.
University of Rochester Medical Center.Overview of multiple pregnancy.
Gabbett MT, Laporte J, Sekar R, et al.Molecular support for heterogonesis resulting in sesquizygotic twinning.N Engl J Med. 2019;380(9):842-849. doi:10.1056/NEJMoa1701313
Centers for Disease Control and Prevention.FastStats - multiple births.
Sahu M, Prasuna JG.Twin studies: A unique epidemiological tool.Indian J Community Med. 2016;41(3):177-182. doi:10.4103/0970-0218.183593
Polderman TJ, Benyamin B, de Leeuw CA, et al.Meta-analysis of the heritability of human traits based on fifty years of twin studies.Nat Genet. 2015;47(7):702-709. doi:10.1038/ng.3285
Monni G, Iuculano A, Zoppi MA.Screening and invasive testing in twins.J Clin Med. 2014;29;3(3):865-882. doi:10.3390/jcm3030865
Johns Hopkins Medicine.Twin pregnancy: Answers from an expert.
American Academy of Pediatrics.Preparing for twins.
American Society for Reproductive Medicine.Challenges of parenting multiples.
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