Core Topics
- How to reduce birth defects and deliver healthy, intelligent infants
- Populations requiring mandatory prenatal diagnosis
- Introduction to Down syndrome, neural tube defects and thalassemia
- Guidance on planned pregnancy
Prenatal Diagnosis for Better Birth Outcomes
Every family hopes to welcome a healthy baby. However, the national incidence rate of congenital defects in China stands at 13.07 per thousand live births, equivalent to one defective infant born every two seconds on average.
During the ten-month gestation, fetal development may develop various malformations due to heredity, environmental pollutants, improper diet, medication, viral infection, maternal-fetal blood group incompatibility and other triggers. Most fetal developmental abnormalities can be identified via clinical examinations during pregnancy. Timely termination of pregnancy for severely malformed fetuses is critical to realize prenatal and postnatal care for superior offspring.
Prenatal diagnosis evaluates fetal health through direct or indirect testing. Commonly adopted techniques are listed below:
1. Ultrasonography
Imaging detects obvious physical fetal deformities and clues of certain hereditary diseases. A comprehensive systematic fetal ultrasound scan is recommended between the 18th and 24th week of gestation.
2. TORCH Screening
Tests maternal infection with rubella virus, cytomegalovirus, herpes simplex virus type I & II and toxoplasma gondii. These pathogens may trigger intrauterine infection and fetal malformation.
Screening window: Pre-pregnancy and early pregnancy.
3. Thalassemia & G6PD Deficiency Screening
These two hereditary disorders are prevalent in southern China, manifesting as anemia and hemolysis in affected children. If both parents carry the same thalassemia gene, there is a 25% risk of severe thalassemia in the fetus. Some severe thalassemia fetuses end in stillbirth; survivors rely on lifelong regular blood transfusions and rarely live beyond school age.
Screening window: Pre-pregnancy and throughout gestation.
4. Screening for fetal chromosomal abnormalities
Serum testing of PAPP-A, AFP, UE3 and β-HCG assesses risks of chromosomal anomalies including Down syndrome, trisomy 18 and neural tube defects.
Screening window: 8–21 weeks of pregnancy.
5. Chorionic villus, amniotic fluid or umbilical cord blood testing
These samples detect chromosomal diseases (Down syndrome, trisomy 18), intrauterine infections (TORCH, parvovirus B19) and hereditary illnesses such as thalassemia, enabling early termination of affected pregnancies to cut birth defects.
- Chorionic villus sampling: 8–11 weeks
- Amniocentesis: 16–21 weeks
- Percutaneous umbilical blood sampling: 22–24 weeks
Who Must Receive Prenatal Diagnosis?
1. Pregnant women aged 35 and above (advanced maternal age)
2. Mothers with a prior delivery of a chromosomally abnormal child
3. Couples where either partner carries balanced chromosomal translocation
4. Women with a history of anencephaly, hydrocephalus, spina bifida, cleft lip/palate or congenital heart disease in previous offspring
5. Carriers of X-linked recessive hereditary disease genes
6. Couples with congenital metabolic disorders or previous affected children
7. Pregnant women with a family history of hereditary diseases or consanguineous marriage
8. Patients with unexplained recurrent miscarriage, stillbirth, malformed fetus or neonatal death
9. Mothers exposed to high-dose chemical toxins, radiation or severe viral infection in early pregnancy
10. Pregnant women with polyhydramnios and suspected fetal malformation
11. Pregnant women with high risk indicated by Down syndrome screening
Down Syndrome (Trisomy 21)
A prevalent chromosomal disorder marked by intellectual disability, protruding tongue, microcephaly, wide eye spacing, flat nasal bridge, simian crease in half of patients, growth retardation and congenital heart disease in over half of cases. Contributing factors include genetics, advanced maternal age and hazardous prenatal exposure. All pregnant women carry a baseline risk of 1 in 600–800 live births; approximately 26,600 infants with Down syndrome are born annually in China, one every 20 minutes. The risk surges sharply for mothers over 35. No curative treatment exists, but prenatal diagnosis allows selective termination for eugenic purposes.
Neural Tube Defects
Main categories: anencephaly, spina bifida and encephalocele. The incidence reaches 0.1%–0.2% in northern China. Over 90% cases are sporadic polygenic disorders resulting from combined genetic and environmental triggers, including teratogenic drugs (anticonvulsants, excess vitamin A), high-temperature exposure, folic acid deficiency and maternal diabetes.
Open spina bifida often causes lower limb paralysis, muscle weakness and incontinence; anencephaly leads to perinatal death; encephalocele is rare but accompanied by severe neurological impairment and intellectual disability.
Maternal serum AFP screening achieves 80%–90% detection for open neural tube defects and over 90% for anencephaly; ultrasonography delivers accurate, reliable diagnosis.
Thalassemia
A hereditary hematological disorder endemic in southern China, with a prevalence close to 10% in Guangdong Province, classified as α-thalassemia and β-thalassemia, each with mild and severe subtypes.
- Severe α-thalassemia: Most fetuses die prenatally or shortly after birth, presenting generalized edema, enlarged abdomen and oversized placenta, known as hydrops fetalis syndrome.
- Severe β-thalassemia: Infants appear normal at birth but gradually develop pallor, apathy, stunted growth, progressive anemia and hepatosplenomegaly within months. Patients depend on lifelong transfusions and rarely survive early adulthood.
- Mild thalassemia: Asymptomatic or with mild anemia in adult carriers.
When two mild thalassemia carriers marry, their children face a 25% chance of being healthy, 50% chance of mild thalassemia and 25% chance of severe thalassemia. Severe α-thalassemia is a major cause of miscarriage and stillbirth; severe β-thalassemia patients rarely live past 20 years old even with treatment, imposing heavy burdens on families and society.
Individuals diagnosed with thalassemia during premarital screening should avoid marrying other thalassemia carriers. Couples carrying identical thalassemia genes must undergo fetal prenatal diagnosis to prevent delivery of severely affected infants.
Planned Pregnancy for Healthy Offspring
Eugenic research confirms fetal health relies not only on intrauterine gestation environment but also pre-conception conditions of sperm and ova. Embryo quality is determined by parental genetics, physical and mental wellness, occupational/living surroundings and nutritional status. Follow these guidelines when planning conception:
1. Avoid pregnancy when either parent is unwell; conceive when both partners are in optimal physical and mental condition.
2. Stay away from toxic environments, hazardous chemicals and radiation for at least 3 months before conception.
3. Refrain from arbitrary medication within 8 weeks pre-conception and throughout pregnancy.
4. Both partners must quit smoking and drinking pre- and post-conception, and avoid secondhand smoke.
5. Limit tea and caffeinated beverages.
6. Delay conception for 6 months after miscarriage and 2 years after cesarean section.
7. Optimal childbearing age: females 24–29 years old, males 24–34 years old.
8. Visit the hospital’s eugenic genetic counseling clinic for pre-conception checkups before planning pregnancy.
9. Apply for a Maternal and Child Health Handbook at the obstetric outpatient department within 80 days (preferably within 2 months) after confirmed pregnancy.