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With the liberalization of the two-child policy, older pregnant women are gradually increasing. Pregnant women over the age of 35 are often asked when doing prenatal examination: amniocentesis or noninvasive DNA examination can be done. Which do you want to do? At this time, pregnant women are often confused.
What is the role of noninvasive DNA examination and amniotic fluid puncture examination and how to choose them? The number of obstetric clinics is huge. Doctors can’t spend a lot of time on detailed explanations. They can only briefly introduce a few words. It’s also difficult for pregnant women to understand comprehensively and make the right choice in a hurry.
“Noninvasive DNA examination and amniocentesis are both means to screen the fetus for chromosome problems.” Huang Dan, chief obstetrician of Beijing Shunyi women’s and children’s Hospital, said that noninvasive DNA examination is safer, cheaper and more convenient, but amniotic fluid puncture is more accurate and comprehensive. With a more comprehensive understanding, we have to make a comprehensive judgment and selection according to their respective economic conditions, the expected value of the fetus and the qualification of the birth inspection unit.
After the age of 35, the quality of female eggs begins to decline, and the probability of fetal malformation gradually increases after pregnancy. Therefore, more attention and accuracy are needed in screening whether the fetus has chromosome problems.
Huang Dan pointed out that the abnormal B-ultrasound examination only observes the appearance of the fetus to see whether the organs that have grown out of the fetus are abnormal or lack some organs that have not yet grown out, which can only reflect structural abnormalities. However, due to the monitoring of blood flow signals, the current B-ultrasound can also reflect some functions, especially the heart, but it is still very limited.
Some people with chromosome problems may not have obvious abnormalities in appearance with ordinary people, but they have problems in intelligence or fertility. Therefore, they should be combined with chromosome examination and abnormal B-ultrasound examination in order to screen out the problem fetus as much as possible.
What are the differences between noninvasive DNA examination and amniocentesis?
Huang Dan introduced that the two inspections have their own advantages and disadvantages in operation methods, inspection timing, inspection content, price, detection rate and others.
Operation method
Noninvasive DNA testing is performed by drawing blood, while amniocentesis is performed by drawing amniotic fluid from pregnant women for culture. Because amniotic fluid needs to be pumped, it is possible to cause infection, abortion and even damage the fetus. The incidence of complications is generally about 0.5%. Usually, amniocentesis will be carried out under the monitoring of B-ultrasound, and its adverse incidence is very low, but it is not equal to 0.
Inspection timing
Noninvasive DNA examination was performed at 12-22 weeks of gestation; Amniocentesis was performed at 16-24 weeks of gestation.
Huang Dan explained that the upper limit time is not because it cannot be tested after this gestational week, but because the older the gestational week, the more difficult it is to deal with problems after screening.
Inspection contents
This is the most common problem of three chromosome screening at present. Sheep wear is to screen 23 pairs (i.e. all) of chromosomes. Noninvasive DNA can only be used as a means of screening, while sheep wear is the means of diagnosis, that is, the gold standard.
Screening price
Noninvasive DNA examination: About 2000-3000 yuan; Amniocentesis: about 2500-7500 yuan.
The price will vary from region to region, and will be adjusted according to the health and economic conditions of each region and the increase or decrease of testing items. The specific price standard issued by the local hospital shall prevail.
Detection rate
Both are high on the whole. The probability of finding problematic fetuses by noninvasive DNA examination is 95% - 99%; Amniocentesis was 99%.
Other
For pregnant women with problems screened out by noninvasive DNA examination, amniocentesis is still needed to make a diagnosis in the next step.
For twin pregnancy, if there is amniotic membrane segmentation between twins, amniocentesis is feasible, because under the positioning of B-ultrasound, it can be very clear which fetus the extracted amniotic fluid belongs to. However, noninvasive DNA examination cannot distinguish which fetus the fetal cells isolated from the mother’s blood belong to, so if one fetus has a problem with DNA and the other does not, it is impossible to know which fetus has a problem.
Amniocentesis has higher requirements for medical personnel and hospitals, so there are relatively fewer hospitals qualified for amniocentesis.
Beijing News reporter Wang kara