How to perform infant screening

Patient's question:

Now the child is six months old. I want to ask the doctor how I can check for deformities.

Doctor's answer:

1. Down Syndrome Screening
Down Syndrome is medically known as trisomy 21, also commonly referred to as congenital idiocy. Only about 4% of congenital idiocy cases are caused by inheritance. In most cases, it is caused by genetic mutations, making it difficult to control the risk of onset. Therefore, screening is necessary to detect it early. Down Syndrome Screening is not a mandatory test. It involves detecting the concentration of alpha-fetoprotein (AFP) and human chorionic gonadotropin (β-hCG) in the mother's blood to check for chromosomal abnormalities in the fetus.
Testing Period: 14 weeks 6 days to 18 weeks 6 days, preferably between 16 and 18 weeks.
2. Ultrasound Anomaly Screening
Testing Period: The pregnant woman should undergo the examination around the 20th week of pregnancy and should not exceed the 28th week.
Examination Items Include: Observing the fetus's nose-lip area and heart to detect most anatomical abnormalities and birth defects, such as anencephaly, hydrocephalus, spina bifida, limb deformities, severe cleft lip and palate, and congenital heart disease.
Around the 24th week, a 3D color ultrasound can clearly display the organs of the fetus, assess fetal growth and development, and observe whether there are any structural abnormalities in the head, limbs, and organs. Additionally, regular checks of the fetal heartbeat and blood pressure are required.
8 Types of Fetal Abnormalities That Ultrasound Cannot Detect
Almost all fetal internal organs undergo continuous growth and changes before birth. Therefore, even if an organ appears normal during early screening, it does not guarantee that it will be normal at birth. Additionally, ultrasound is limited by the mother's abdomen and the uterus, making it impossible to adjust the fetus's position or obtain images from certain angles. President Sun Sansuan pointed out the following situations where ultrasound examination is limited due to fetal growth conditions:
1. Hydrocephalus: Many hydrocephalus or hydronephrosis conditions only gradually develop in the later stages of pregnancy.
2. Complete Blindness: Since there is no light stimulation in the uterus, the fetus's eyes remain closed, making it impossible to diagnose conditions like congenital complete blindness or microphthalmia.
3. Hearing: By the time the fetus is 5–6 months old, its hearing has developed. However, there is currently no method to determine whether the fetus has congenital hearing impairment.
4. Congenital Heart Disease: The atrial septal defect (foramen ovale) and ductus venosus in the heart gradually close after birth. Although these heart diseases can be easily diagnosed at birth, they cannot be detected before birth.
5. Gastrointestinal Obstruction: Gastrointestinal obstructions are rarely present before the 24th week of pregnancy because the fetus rarely swallows large amounts of amniotic fluid in the early stages of pregnancy.
6. Limb (Finger/Toe) Terminal Abnormalities: Abnormalities such as inward or outward deviation of hands and feet, polydactyly, syndactyly, or missing finger joints are almost impossible to diagnose accurately with ultrasound due to the fetus's frequent clenched fist position.
7. Dwarfism: Some dwarfism symptoms cannot be detected early because fetal bone growth and development gradually stop between 6–7 months of age.
8. Congenital Metabolic Disorders: Most metabolic and biochemical disorders, such as mucopolysaccharidoses, only manifest after the baby begins to eat after birth. As a result, many lethal metabolic disorders cannot be identified before birth unless the mother has previously given birth to a child with a similar condition.
3. Amniocentesis
Testing Period: 16–22 weeks
Amniocentesis is a procedure where a thin, long needle is guided by an ultrasound probe to pierce the abdominal wall, uterine muscle layer, and amniotic membrane to extract 20–30 ml of amniotic fluid. This fluid is then used to examine fetal cells for chromosomal, DNA, and biochemical components. It is currently the most commonly used prenatal diagnostic technique. The procedure is simple, does not require anesthesia before the puncture, and does not require hospitalization.