These figures indicate that, in a group of 1000 babies with Down syndrome, some 14 or 15 babies will be a twin or a triplet, with their other twins/triplets unaffected, and 2 or 4 babies will be identical twin pairs, both with Down syndrome.
Mirror image: Identical twins are believed to be genetically identical, but one twin can have mutations not shared by the other. Identical twins can be genetically different, which could explain why they do not always share disorders such as schizophrenia or autism, according to a study published in March in PLoS One.
A large population-based study in Europe suggests that at any age, a woman is 32% rather than 100% more likely to have at least one baby with DS in a DZ twin pair compared to singletons, suggesting that babies who are DZ twin with Down syndrome are less likely to survive to diagnosis (3).
Not necessarily. Identical twins may differ on a host of diseases and conditions. According to Haseley, “If a genetic change occurs in a gene that affects its function, health concerns may arise.” Twins may differ in their risk of cancer, rheumatoid arthritis, or other conditions.
Some cases were diagnosed by both methods. The researchers determined a 96% chance that if one twin has ASD, the other has it, too. However, symptom scores varied greatly between twins diagnosed with ASD.
If one identical twin has autism spectrum disorder (ASD), the other twin has a 76 percent chance of also being diagnosed with it. The numbers are lower for fraternal twins.
Multiples are about twice as likely as singleton babies to have birth defects, including neural tube defects (such as spina bifida), cerebral palsy, congenital heart defects and birth defects that affect the digestive system.
Vanishing twin syndrome was first recognized in 1945. This occurs when a twin or multiple disappears in the uterus during pregnancy as a result of a miscarriage of one twin or multiple. The fetal tissue is absorbed by the other twin, multiple, placenta or the mother. This gives the appearance of a “vanishing twin.”
An ultrasound can detect fluid at the back of a fetus's neck, which sometimes indicates Down syndrome. The ultrasound test is called measurement of nuchal translucency. During the first trimester, this combined method results in more effective or comparable detection rates than methods used during the second trimester.
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.
Because identical twins come from the exact same combination of egg and sperm, they have exactly the same combination of chromosomes. A DNA test would reveal that they have over 99.9% identical DNA.
Scientists have shown that identical twins have very similar marks when they are born. But, as they age, the marks in their DNA become more and more different. So even though identical twins have the same DNA, they are using it in different ways.
These factors include geographic region, maternal education, marital status, and Hispanic ethnicity. Because the likelihood that an egg will contain an extra copy of chromosome 21 increases significantly as a woman ages, older women are much more likely than younger women to give birth to an infant with Down syndrome.
A Detailed Anomaly Scan done at 20 weeks can only detect 50% of Down Syndrome cases. First Trimester Screening, using bloods and Nuchal Translucency measurement, done between 10-14 weeks, can detect 94% of cases and Non-invasive Prenatal Testing (NIPT) from 9 weeks can detect 99% of Down Syndrome cases.
Such twins, known scientifically as 'MoMo', an abbreviation for monoamniotic-monochorionic, are some of the rarest types of twins, making up less than one percent of all births in the United States, noted the statement. It also stressed that such MoMo twin pregnancies have a high risk of fetal complications.
The donor twin is smaller because he or she sends blood to the co-twin. As the disease progresses, the donor will produce so little urine that its bladder may not be seen on ultrasound. The amniotic membrane will wrap around the baby, known as a “stuck” twin.
The highest risk twin gestation is called monochorionic/monoamniotic, where identical twins share a placenta and an amniotic sac. In addition to the possibility of developing twin-to-twin transfusion syndrome, these babies are at high risk for cord entanglement.
Risk of Prematurity
Twin pregnancies have a higher risk for prematurity, which means birth that occurs after 20 weeks but before 37 weeks gestation. Just 40% of twin pregnancies go full term. The average twin pregnancy is 35 weeks, compared to the average singleton pregnancy, which is 39 weeks.
The incidence of handicap was 3.7% in twins, 8.7% in triplets, 11.1% in quadruplets, and 10.0% in quintuplets. The risk of producing at least 1 handicapped child was approximately 1 in 13 pairs of twins (7.4%), 1 in 4 or 5 sets of triplets (21.6%), and 1 in 2 sets of quadruplet and quintuplets (50%).
Identical twins are more likely than fraternal twins to get the same illness. If one of a pair of identical twins is diagnosed with a particular disease or health condition, like high blood pressure, the other twin should be checked often for early symptoms.
In identical twins, if a twin develops schizophrenia, the other twin has a 1 in 2 chance of developing it, too. This is true even if they're raised separately. In non-identical twins, who have different genetic make-ups, when a twin develops schizophrenia, the other only has a 1 in 8 chance of developing the condition.
The rate of Down syndrome for both maternal and paternal age greater than 40 years is approximately 60 per 10,000 births, which is a six-fold increase compared with maternal and paternal ages less than 35 years of age. In this age group, the paternal contribution to Down syndrome was 50 percent.