Seeing a friend asking "Can 4D ultrasound rule out Down's syndrome?" This is a big deal, so don't get these peculiar ideas just to save a labor and delivery test.
The answer is yes, the 4D ultrasound can't rule out Down's syndrome. The purpose of the 4D ultrasound is not to rule out Down's syndrome, but to rule out the possibility of structural malformations in the fetus, that is to say, malformations of the physical appearance.
Although some Down's babies are characterized by a lack of nasal bone, anencephaly, spina bifida, heart abnormalities, kidney abnormalities, intestinal abnormalities, skin folds on the hands, cracked eyes, and many other possibilities. However, many Down's babies do not have obvious structural markers and still require Down's screening to be screened.
In view of the misunderstanding of many friends about the maternity test, we might as well introduce what are the maternity tests that need to be done to rule out fetal anomalies during the whole pregnancy?
Ultrasound medical device
NT testWhen: At 11 weeks to 13 weeks + 6 days.
Method: It is done by scanning the thickness of the fetal nuchal translucency band by ultrasound. If the thickness is greater than 3mm, it suggests that there is a higher risk of having Down syndrome and further invasive testing is needed, as well as an ultrasound to rule out cosmetic malformations. Invasive tests are usually amniocentesis.
Accuracy: 80%
Down's syndrome screeningWhen: It is done between 16 and 18 weeks.
Methods: It is done by taking the pregnant woman's venous blood, checking three items such as AFP, HCG and E3, and then combining them with the week of gestation, expected date of birth, age and other indexes to comprehensively determine the risk of Down's syndrome babies.
Accuracy: 65% (inaccurate for twins).
Down syndrome screening
Non-invasive DNAWhen: At 16 weeks to 18 weeks. (If the Down's syndrome screening high risk must do non-invasive DNA, if the advanced maternal age, have a family history of Down's syndrome, work in harmful environments, taking drugs that may cause teratogenicity, etc. directly do non-invasive DNA.)
Methods: Through the extraction of pregnant women's blood in a vein, the use of gene amplification to check the trisomy 21, 18, 13 cells, through the chromosomal presence or absence of abnormalities to determine the risk of a fetus having Down syndrome.
Accuracy: 99% (accuracy decreases significantly with twins)
AmniocentesisWhen: 16 weeks to 18 weeks (non-invasive DNA high risk, NT high risk to do amniocentesis).
Methods: Using a puncture needle, and with the assistance of ultrasound, fetal skin tissue is aspirated from the amniotic fluid and, after tissue culture, directly analyzed for chromosomal abnormalities to more accurately determine the risk of a fetus with Down syndrome. Of all the risk determinations for Down's syndrome, only amniocentesis is the gold standard.
Accuracy: 99%
4D macrosomiaTime: It is performed at 20 weeks to 28 weeks, with the best time being 22-24 weeks.
Methods: Through 4D ultrasound, it visualizes the appearance of the fetus' structure for any deformities, mainly including the head, face, internal organs, limbs, spine and so on. Appearance deformities such as anencephaly, hydrocephalus, spina bifida, harelip, etc. can be easily detected.
Accuracy: >80%.
All in all, each time period of the examination has a different significance, 4D ultrasound can not cover the Down's syndrome, Down's syndrome can not replace the 4D ultrasound, it is recommended to not miss any pregnancy test. What do you think? Let's discuss.