From the beginning of pregnancy, expectant mothers need to undergo many examinations, including B-ultrasound, Down syndrome screening, etc. If the risk of Down\’s syndrome is high or the B-ultrasound results are abnormal, most doctors will recommend prenatal diagnosis. But there are many methods of prenatal diagnosis. Which method should expectant mothers choose? Which method is safer? Which method is more reliable for diagnosis? Professor Li Weijing, director of the Department of Fetal Medicine at the First Affiliated Hospital of Jinan University, reminded expectant mothers that different diagnostic methods should be used at different stages of pregnancy, but examinations should be carried out as early as possible to avoid missing the best examination time.
Different diagnostic techniques are suitable for examinations at different times
Professor Li Weijing said that with the advancement of prenatal diagnosis technology, there are more and more methods for intrauterine fetal diagnosis, but no matter which method, fetal samples must be obtained. There are three main methods currently used for prenatal diagnosis: chorionic villus puncture, amniocentesis and umbilical cord blood puncture.
Chorionic villus puncture is suitable for the diagnosis of chromosomal abnormalities such as Down syndrome in early pregnancy (11-14 weeks). The diagnosis can be confirmed by obtaining placental tissue through puncture.
Amniocentesis is indicated for prenatal diagnosis of abnormalities such as Down syndrome between 16 and 24 weeks of gestation.
Cordocentesis is a diagnostic procedure that can be performed any time after 20 weeks of pregnancy.
Which diagnostic method is safer
Which of the three commonly used prenatal diagnosis methods is safer? Professor Li Weijing said that in comparison, chorionic villus puncture is the safest, because puncture punctures the placenta rather than the fetus, and the puncture needle does not enter the amniotic cavity, the environment where the fetus lives, so it basically has no impact on the fetus. But that doesn’t mean there are no risks at all. Chorionic villus aspiration carries the same risk of infection as regular injections, and infection can lead to miscarriage. For skilled doctors, the incidence of this infection is about 0.1%-0.5%.
Both amniocentesis and umbilical cord puncture enter the amniotic cavity, so the risk of miscarriage or infection is relatively high, about 0.5%-1%. Both methods pose the same risks to the mother and fetus, but cord puncture requires more skill from the doctor.
Which diagnostic method is more reliable?
If it is the result of long-term practice, the results of the three methods are also reliable; if it is rapid culture (FISH culture), the error of the villus results is larger than the other two methods. But because the final result is the result of long-term practice, there is no obvious difference between the three methods. Some abnormal chromosomes need to be examined in different specimens. For example, for trisomy 16, only amniotic fluid specimens can be diagnosed, and the results of other specimens are negative.
Finally, Professor Li Weijing emphasized that once an expectant mother is found to be at high risk for Down\’s syndrome or has an abnormal ultrasound examination, or is asked by a doctor to undergo prenatal diagnosis, she must be examined as soon as possible.
Expert profile: Li Weijing, female, chief physician,Associate professor, master\’s tutor. He works in the Department of Fetal Medicine, the First Affiliated Hospital of Jinan University. He is the only expert in China who holds the internationally recognized British Fetal Medicine Foundation\’s prenatal diagnosis qualification certificate. He is engaged in both obstetric clinical work and morphological prenatal diagnosis.