What Does a Baby With Down Syndrome Look Like on Ultrasound
Downward syndrome (trisomy 21) can be diagnosed almost as presently every bit a baby is born, based on distinctive physical characteristics that prompt immediate testing. Down syndrome can also be diagnosed, or at least suspected, based on whatsoever of several prenatal tests including a nuchal translucency screening, sonogram, quadruple screen, or other claret tests. Here is how Down's syndrome is diagnosed in both scenarios.
Imaging
Mod imaging techniques can provide very detailed pictures of what's going on inside of the body, including features of a still-developing fetus. Since many characteristics of Down syndrome are visible, information technology'southward possible to pick up on some of them in an ultrasound before a baby is born.
While imaging tests can help indicate the possibility of Downwardly syndrome, they cannot confirm information technology. Likewise, a negative examination does non rule out Down's syndrome.
Nuchal Translucency Ultrasound Screening
This specialized ultrasound, which is performed at 11 to 13 weeks, measures the thickness of an area of tissue at the back of a fetus'due south neck called the nuchal fold. Though this test is recommended for all pregnant women, this is a difficult measurement to obtain and merely someone who has been specifically trained and certified to perform this screening can practise it.
In general, a measurement nether three millimeters (mm) is considered normal (or screen negative) and one that's over three mm is considered abnormal (or screen positive). In the latter instance, information technology will be important to run across with a genetic counselor to talk over your screening results, what they mean, and your diagnostic testing options such equally chorionic villi sampling (CVS) or amniocentesis (encounter below).
Ultrasound (Sonogram) Screening
Ultrasounds work by using sound waves to generate an epitome of the fetus. These waves pose no risk to mother or baby. The standard ultrasound is done between xviii and 22 weeks of pregnancy and can reveal a variety of concrete characteristics that are associated with an increased gamble that a developing babe has Down syndrome.
The healthcare provider will rub a special gel on your belly and so slide a transducer, a wand-like apparatus that transmits audio waves into your abdomen, over your belly. The audio waves travel through the amniotic fluid, deflecting off of structures located in the uterus. The speed at which the waves bounciness dorsum differs depending on the density of what they hitting. A computer turns this information into an image of the fetus. The harder or denser a structure is, the brighter it will show upward on the monitor.
Occasionally, but not always, infants with Down's syndrome show subtle signs, called soft markers, on an ultrasound that suggest they may have Down syndrome:
- A shorter-than-normal femur (thigh) os
- A missing nose os in the first trimester
- Duodenal atresia: This abnormality of the duodenum, a part of the minor intestine, will testify up on an ultrasound equally a double bubble caused by extra fluid and swelling in the duodenum and stomach. Duodenal atresia sometimes may exist detected equally early equally 18 to 20 weeks, but usually isn't seen until after 24 weeks. Another sign of duodenal atresia in pregnancy is excessive amniotic fluid. If a duodenal atresia shows up in an ultrasound, there is a xxx% chance that the baby will have Downward syndrome.
- Certain heart defects
- Gastrointestinal blockages
These signs exercise not mean that a babe has Down's syndrome for sure. Again, further testing is needed to ostend the diagnosis.
Likewise, information technology is important to note that nigh fetuses with Down's syndrome show no abnormalities on ultrasound, which can be falsely reassuring to parents who are especially concerned about this disorder.
Maternal Blood Tests
Information technology's of import to know that blood tests are used for screening and, like imaging tests for the status, only indicate the level ofpossibilitythat a child has Down syndrome.
Negative screening results mean that your chance of having a baby with Down syndrome is low, simply they do non guarantee there are no birth defects. If you lot have a negative upshot, you likely will non be offered follow-up diagnostic testing.
Positive screening results hateful the chances a fetus has Down syndrome are higher than normal, and so follow-up diagnostic testing will be offered. That said, nigh women with screen positive results volition take normal salubrious babies.
Quadruple Screen
This maternal blood test, which is part of routine prenatal care for all expectant moms, typically is performed between the 15th and 18th weeks of pregnancy. It measures levels of 4 specific substances. Two of these happen to exist associated with Down syndrome:
- HCG (homo chorionic gonadotropin):HCG is a hormone made by the placenta. In fact, very early on in pregnancy, it'due south the substance used to detect pregnancy in dwelling pregnancy tests, since information technology too shows up in urine. HCG levels in the blood of women carrying babies with Down syndrome tend to exist higher than average.
- PAPP-A (pregnancy-associated plasma protein A): A adult female with a depression blood level of PAPP-A has an increased chance that her babe will accept Down syndrome. Low levels of PAPP-A also may indicate an increased risk for intrauterine growth brake, premature commitment, preeclampsia, and stillbirth.
Prenatal Jail cell-Free DNA Screening (cfDNA)
This relatively new examination extracts Dna from both mother and fetus using a sample of the female parent'southward blood and screens for chromosome problems such as Downwards syndrome (besides equally trisomy 13 and trisomy eighteen). Information technology can be done equally early in pregnancy equally ten weeks but is not routinely done.
According to the American College of Obstetricians and Gynecologists (ACOG), healthcare providers will recommend cfDNA merely for women with certain run a risk factors for fetal defects, including advanced maternal historic period (35 or over); a fetal ultrasound that shows an increased run a risk of chromosome abnormality; a previous pregnancy with a trisomy; a positive first- or 2d-trimester maternal screening test; or a known balanced chromosome translocation in the mother or father.
It's important to empathize that cfDNA testing tin can only indicate if a fetus is at an increased adventure for a chromosome problem or is unlikely to have one. It is not a diagnostic test. Information technology also is expensive, although the examination may be covered by health insurance for women of advanced maternal age.
While these screenings can be helpful, the only way to definitively diagnose Downwards syndrome is to become a diagnostic test.
Diagnostic Tests
If a prenatal screening test indicates in that location's a possibility your child volition take Down syndrome or if you lot have adventure factors for having a kid with the disorder, then you may exist faced with taking the next step and confirming the diagnosis. This is an extremely personal decision, one that'south fraught with dueling emotional and practical implications.
Deciding Whether to Have a Confirming Examination
It can exist helpful to ask yourself very specific questions about whether prenatal testing to confirm a diagnosis of Downwardly syndrome (or whatever birth defect) is the correct thing for you and your family unit. For instance, yous'll want to consider your ain personality: Do you lot handle things better when y'all know what to expect? Or would knowing that you lot're conveying a child with trisomy 21 cause yous overwhelming anxiety?
In businesslike terms, would knowing ahead of time let you to set for the potential health problems your baby with Downwardly syndrome may exist born with? And, as hard as this scenario is to think about, would learning yous take a child with a nascence defect crusade you to consider terminating the pregnancy?
Exist open about your thoughts when speaking with your healthcare provider and know that getting a diagnostic test is entirely your choice.
Down syndrome Doctor Give-and-take Guide
Go our printable guide for your next healthcare provider's date to help yous ask the right questions.
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Karyotyping
If you lot decide to motion forward with diagnostic testing, amniocentesis and chorionic villi sampling volition be offered to you. Tissue retrieved with either of these procedures will be karyotyped.
A karyotype is an analysis of a baby'southward genetic makeup that looks at the number of chromosomes he or she has under a microscope.
Under normal circumstances, in that location are 46 chromosomes organized in 23 pairs. Chromosome pairs are numbered one through 23. In the instance of Down syndrome, at that place is an extra chromosome in the 21st spot, meaning in that location are 3 of this particular chromosome. (This is why the clinical proper name for Down syndrome is trisomy 21.)
A karyotype tin can be done using most any type of cell. When a diagnosis is being confirmed after nativity, for instance, the cells normally are taken from a sample of the baby's blood. During pregnancy, karyotyping tin can be done by performing ane of the following tests. Neither of these is considered a routine office of prenatal care, although they often are recommended for women who are 35 or over or who have other chance factors for having a child with a chromosomal abnormality.
- Amniocentesis:This examination, which is done betwixt weeks 15 and 20 of pregnancy, creates a karyotype using a sample of amniotic fluid. A healthcare provider uses an ultrasound to aid guide a long, thin needle into a woman'southward abdomen and through to the uterus in order to excerpt a sample of fluid from the amniotic sac. This fluid contains skin cells that accept sloughed off of the fetus, which will and then exist tested.
Information technology takes just a few moments to excerpt amniotic fluid, but most women do written report feeling some discomfort and mild cramping. Amniocentesis is relatively safe: It carries a 1-in-400 risk of causing miscarriage. The process of culturing the cells so that they tin can be karyotyped tin can have up to two weeks. - Co-ordinate to the National Down's syndrome Society (NDSS), the test is nearly 100 pct accurate in diagnosing Downward syndrome prenatally. What's more, it can distinguish betwixt complete trisomy 21, translocation Down syndrome, and mosaic Down's syndrome.
- Chorionic Villi Sampling (CVS):As with amnio, CVS testing uses karyotyping to diagnose Downwards syndrome. However, the cells examined are taken from structures in the placenta chosen chorionic villi.
CVS is performed at 11 to 13 weeks of pregnancy and is done in one of two ways: Either a needle is inserted directly into the abdomen or is threaded through the cervix (much similar having a Pap smear). - The insertion of the needle tin be painful, but the procedure is very quick. CVS poses the same minor risk of miscarriage as amniocentesis, is virtually 100 percentage accurate, and is able to reveal which blazon of trisomy 21 a baby has. It usually takes a couple of weeks for total results from CVS testing to be finalized.
FISH Testing
Fluorescent in situ hybridization (FISH testing or FISH analysis) is a relatively new technique that can determine how many copies of a detail chromosome a prison cell has. It'south usually done using the same tissue sample from an amniocentesis or CVS test.
To perform a FISH analysis, colored dyes are used to highlight sure chromosomes, which makes it possible to count them. 1 advantage of using FISH assay rather than karyotyping is that information technology isn't necessary to civilization cells before analyzing them. This means results can be available in a few days rather than a few weeks.
A disadvantage of FISH is that unlike karyotyping, it just can reveal if there is an extra chromosome 21. It doesn't offer information nearly the structure of the chromosomes that would be needed to identify Down syndrome as complete, mosaic, or translocation trisomy 21. The differences in these types affect the severity of the status and the likelihood of conceiving another child with Down syndrome.
Physical Exam
Down syndrome is usually quite evident as soon as a baby with the disorder is born, every bit many of its distinctive physical characteristics are present at birth. These include:
- A circular confront with a flat profile and small facial features (nose, oral fissure, ears, and optics)
- Protruding natural language
- Almond-shaped upturned eyes with epicanthus folds
- White flecks in the colored part of the eyes (Brushfield spots)
- A short neck and a small head that's somewhat apartment in the back (brachycephaly)
- A single crease beyond the palm of each hand (normally there are ii), short chubby fingers, and a pinky finger curves in—a condition called clinodactyly
- Minor feet with a larger than normal space betwixt the big and second toes
- Hypotonia, or low muscle tone, which causes the newborn to appear "floppy" due to a condition called hypotonia.
These characteristics are red flags that a newly born baby has Down syndrome. To confirm the diagnosis, a claret sample will be taken and used to create a karyotype.
Source: https://www.verywellhealth.com/diagnosing-down-syndrome-1120396
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