Since becoming pregnant, the healthy development of your baby has become your top priority. We undergo numerous prenatal checkups during pregnancy, many of which are designed to monitor fetal growth. Below, let's explore specific prenatal tests that can detect fetal abnormalities.
Fetal Abnormalities Cannot Escape These Professional Tests (Public Health Network)
Down Syndrome Screening·Timing: 14 weeks 6 days to 18 weeks 6 days, ideally between 16 and 18 weeks.
·Purpose: Down syndrome screening analyzes the mother's blood to assess the risk of the fetus having Down syndrome.Children with Down syndrome often experience severe intellectual disabilities alongside other issues such as congenital heart disease, leukemia, and digestive tract malformations. They typically cannot care for themselves and have a shortened lifespan, with an average survival age of 20–30 years and an IQ generally ranging from 20 to 50.
· How accurate is the Down syndrome screening?
The screening can detect 60-70% of fetuses with Down syndrome. It's important to note that screening only indicates the likelihood of Down syndrome in the fetus; it cannot definitively confirm the condition.
· Why perform Down syndrome screening?
Serum screening is an effective method for detecting Down syndrome, as any pregnant woman can carry a fetus with the condition.80% of Down syndrome cases occur in women under 35. Down syndrome screening helps narrow the scope for amniocentesis while ensuring no high-risk pregnancies are overlooked. It is recommended for all pregnant women to undergo screening as a preventive measure.
Chorionic Villus Sampling (CVS) · Timing: The optimal window for CVS is between 10–12 weeks of pregnancy.
· Purpose: To assess fetal health and enable appropriate intervention if abnormalities are detected. If maternal factors cause fetal issues—such as gestational hypertension potentially leading to growth restriction—maternal health management can be adjusted to support normal fetal development. However, certain congenital abnormalities cannot be improved through maternal interventions.
· Procedure: Chorionic villus sampling involves obtaining a small sample of placental tissue from the mother's uterus.First, an ultrasound determines the placenta's location and the fetus's gestational age. Based on the placenta's position, the sampling method is selected. One approach involves inserting a flexible, thin catheter through the vagina and cervix into the developing placenta (transcervical method). The other involves inserting a thin needle through the abdomen into the placenta (transabdominal method) to obtain a small sample of chorionic villi tissue for analysis. The transcervical method is generally preferred.
· What is the accuracy rate of chorionic villus sampling?
Chorionic villus sampling has a high accuracy rate, reaching 99%. However, in rare cases, further amniocentesis may be required.
· Who needs chorionic villus sampling?
Not all expectant mothers require this procedure. It may be recommended in the following situations:
- Women over 35 years old who wish to know early if the fetus has chromosomal abnormalities.
- Women who have previously given birth to a child with birth defects.
- Those with a family history of genetic disorders.
Amniocentesis·Timing: 16–24 weeks of pregnancy
·Purpose: Amniocentesis primarily helps doctors diagnose fetal abnormalities, such as neural tube defects, chromosomal abnormalities, or genetic disorders.· Procedure: Under ultrasound guidance, a thin needle is inserted through the mother's abdomen and uterine wall into the amniotic cavity to extract fluid for analysis. · Who requires amniocentesis? Though medically validated, amniocentesis carries inherent risks due to factors like inadequate pre- or post-procedure care.Therefore, it is not performed universally but only when medically indicated. This includes the following groups:
1. Pregnant women aged 35 or older.
2. Expectant mothers with high-risk Down syndrome screening results.
3. Women with a history of delivering infants with congenital abnormalities, particularly chromosomal abnormalities.
4. Couples where one partner has chromosomal abnormalities or balanced translocations.
5. Women who are carriers of X-linked genetic disorders and require knowledge of the fetus's sex during mid-pregnancy.
6. Pregnant women with specific obstetric histories or serum abnormalities. This includes those who have previously delivered babies with neural tube defects or who have elevated alpha-fetoprotein levels in their serum during pregnancy.
Umbilical Cord Blood Testing·Timing: 20 weeks to before delivery
·Purpose: Fetal umbilical cord blood can be tested for chromosomal abnormalities, genetic conditions, biochemical functions, hemoglobin levels, coagulation function, hypoxia status, and viral infections.
·Method: In addition to storage at birth, fetal umbilical cord blood can also be tested during pregnancy.Umbilical cord blood testing is an invasive procedure. Primarily guided by ultrasound, fetal umbilical cord blood is extracted through the mother's abdomen for analysis.
·Testing Process
(1) Biochemical analysis of the supernatant monitors fetal maturity or detects certain congenital malformations, particularly neural tube defects such as anencephaly or hydrocephalus;(2) Cellular components undergo chromosomal analysis, enzyme biochemical testing, and sex determination to predict or confirm fetal gender. This aids in diagnosing chromosomal abnormalities, genetic disorders, and congenital metabolic defects.
· Who Should Undergo Umbilical Cord Blood Testing?
Umbilical cord blood testing carries inherent risks, so strict indications apply during pregnancy.However, for older pregnant women, this test is highly recommended.
Fetal Ultrasound·Timing: Throughout the entire pregnancy. The three scheduled fetal ultrasound appointments in the maternal handbook are: the first prenatal checkup to confirm fetal heartbeat, the second between 20–22 weeks, and the third around 30–32 weeks.· Purpose of the Test: Fetal ultrasound examines the external structures of the fetus. It primarily screens for structural abnormalities such as cleft lip/palate, spina bifida, abdominal wall defects, or malformed fingers/toes. If structural abnormalities are detected, they may indicate potential genetic or chromosomal deficiencies.
· How accurate is fetal ultrasound?
Ultrasound examinations are not 100% accurate and face several limitations. Factors like excessive abdominal fat in the mother or fetal positioning that obscures certain organs can hinder interpretation. Amniotic fluid volume also affects the accuracy of ultrasound findings.· Can ultrasound examinations harm the mother or fetus?
Excessive or frequent ultrasounds in early pregnancy, especially recording videos of the fetus, cannot guarantee absolute safety. However, when performed under medical guidance following standard protocols, the risk of harm to both mother and baby is extremely low.