how rare is it to have twins with down syndrome?
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If we consider all births, we estimate that identical twins with Down syndrome occur at the rate of 1 or 2 in a million pregnancies and non-identical twins at the rate of 14/15 in a million.
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Down syndrome is an example of a condition caused by trisomy. People with Down syndrome typically have three copies of chromosome 21 in each cell, for a total of 47 chromosomes per cell. Monosomy, or the loss of one chromosome in cells, is another kind of aneuploidy.
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Contrary to popular belief, your chances of having monozygotic twins are not related to your family history. If there is more than one set of identical twins in a family, it is more likely due to luck or external environmental factors—but not family genetic history.
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The chances of having identical twins is relatively rare — around 3 or 4 in every 1,000 births. And while it may be obvious, identical twins are always the same sex, either both boys or both girls, at birth. Why? Well, they don't just look alike — they also share the exact same DNA.
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1 in 85 in general. 1 in 250 to have identical twins. 1 in 17 if the mother is a fraternal twin. 1 in 85 if the mother is an identical twin.
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Fraternal -- or dizygotic -- twins form from two eggs that have been fertilized by two of the father's sperm, producing two genetically unique siblings. They share 50% of their DNA. But "semi-identical" twins are so rare, experts say they have only identified two cases -- ever.
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Babies with Down syndrome are more likely to be born prematurely. Their birth weight and length may be below average.
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Twins and handedness. Left-handedness always occurs at a lower frequency than right-handedness. Generally, left-handedness is found in 10.6% of the overall population. Some studies have reported that left-handedness is more common in twins than in singletons, occurring in 21% of people who are twins.
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22, 2007 — -- The chances of having quadruplets is about one in 800,000. The chances of having a set of identical quadruplets is one in 11 million to 15 million. On Aug. 12, four babies beat the odds and broke a record at the same time.
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Identical twins The first involves a single egg being fertilized by a single sperm. ... But then, somewhere along the way, the fertilized egg divides into two, resulting in identical twins. The chances of having identical twins is relatively rare — around 3 or 4 in every 1,000 births.
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How common are twins? Twins are relatively uncommon. According to the American Society for Reproductive Medicine (ASRM), only approximately one in 250 pregnancies results in twins.
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The first involves a single egg being fertilized by a single sperm. Reproduction 101, right? But then, somewhere along the way, the fertilized egg divides into two, resulting in identical twins. The chances of having identical twins is relatively rare — around 3 or 4 in every 1,000 births.
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Monoamniotic twins are rare, with an occurrence of 1 in 35,000 to 1 in 60,000 pregnancies.
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The chances of having identical twins is relatively rare — around 3 or 4 in every 1,000 births.
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If your first set of twins were fraternal, then your chances of having another set of fraternal twins is multiplied by four! That's 1 in 12! If your first set of twins were identical, then your chances of having another set of identical twins drops way down to 1 in 70,000 or so.
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All pregnant women have the same chance of having identical twins: about 1 in 250. Identical twins do not run in families. ... older mothers are more likely to have non-identical twins because they're more likely to release more than 1 egg during ovulation.
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Genetics can definitely play a role in having fraternal twins. For example, a woman that has a sibling that is a fraternal twin is 2.5 times more likely to have twins than average! However, for a given pregnancy, only the mother's genetics matter.