Is it possible to have boy and girl conjoined twins

National Human Genome Research Project. Fraternal twins. Identical twins. National Library of Medicine. Is the probability of having twins genetic?

American Academy of Pediatrics. The difference between identical and fraternal twins. Updated November 7, Impact of conception method on twin pregnancy course and outcome. Geburtshilfe Frauenheilkd. Monozygotic twins of opposite sex. Cytogenet Cell Genet. PMID: Y Chromosome in Tumer syndrome; a case report. Images Paediatr Cardiol. Monochorionic-diamniotic twins discordant in gender from a naturally conceived pregnancy through postzygotic sex chromosome loss in a 47,XXY zygote.

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I Accept Show Purposes. Table of Contents View All. Table of Contents. Identical Twins. Fraternal Twins. Exception to the Rule. Genetically Dissimilar. Was this page helpful? Thanks for your feedback! Sign Up. What are your concerns? Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles.

Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. In fact, you might not even recognize the smaller twin as a separate individual. A milder version of this is called twin to twin transfusion syndrome TTTS.

Acardiac twins experience a more extreme form of TTTS that may result in developmental issues for the fetuses. Treatments like surgery can improve outcomes, according to research.

In semi-identical twins, two separate sperm fertilize one egg. The fertilized egg then splits in two. So, semi-identical twins share all the same chromosomes from their birthing parent, but only about 50 percent from their non-birthing parent. Sometimes identical twins can be assigned the sex of male and female at birth. These twins start off as identical males with XY sex chromosomes. But shortly after the egg divides, a genetic mutation called Turner syndrome occurs, leaving one twin with the chromosomes X0.

This twin will be assigned female at birth but may have developmental issues, as well as difficulties with fertility later in life, according to the National Health Service. Once a person becomes pregnant, their body stops releasing new eggs for potential fertilization — except in some rare cases. A phenomenon known as superfetation can occur when a second egg gets released and fertilized after a person is already pregnant.

In this case, both fertilized eggs will develop, but one twin will be slightly older than the other. This is known as heteropaternal superfecundation — a common occurrence in animals but very rare in people. Twin pregnancies often come with an increased risk of developing some medical conditions. These can include:. A twin pregnancy has risks of complications, so parents should make sure to receive good prenatal care and seek medical attention for any concerns.

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A new study finds that epidurals do not affect child development in their later years. A fetal arrhythmia is an irregular heart rate — too fast, too slow, or otherwise outside the norm. It's often benign. The surviving cells would go on to combine together and then divide again into the two twins. In addition, the girl and boy each have male and female sex chromosomes — in other words, each twin has some cells that carry an XX pair female and some that carry an XY pair male.

Having both male and female pairs of sex chromosomes throughout various cells in the body is linked to certain developmental problems in the reproductive organs as well as cancer, Gabbett said.

When the doctors examined the girl twin's ovaries, they found some changes linked to cancer , and so "the difficult decision was made to remove them so she didn't develop cancer," he said.

The girl also developed a blood clot shortly after she was born — blood clots are a common complication for identical twins in general — and the clot cut off the blood supply to her arm. As a result, doctors also had to amputate her arm. There is good news, however: The twins are now 4 and a half years old and are otherwise developing normally, Gabbett said.

To get a better understanding of how rare sesquizygosis twins are, the researchers went on to examine the genes of nearly 1, other twins and didn't find another case of semi-identical twins, nor did they find evidence of the condition in a previous study from another research team that examined DNA from more than 20, twins.

Still, it's possible that there are cases doctors have missed: Unless the twins are different genders, sesquizygotic twins could be missed, because people might just assume they're identical twins, Gabbett said. Even so, we "believe this is so rare that routine testing is not warranted," Gabbett said. Only one other case in the world has been reported, to their knowledge, Gabbett said.