Many mothers, after learning that they are pregnant, worry whether their baby in the womb will be healthy or have disabilities. Currently, there are several methods to detect abnormalities in the fetus.
Fetal abnormality screening has been developed for the safety of both mother and baby, such as high-frequency sound wave examination (ultrasound) to detect physical disabilities of the fetus, and genetic Down syndrome screening by amniocentesis to test chromosomes and measure the amount of Alpha-fetoprotein (AFP) to check for brain and spinal cord abnormalities in the fetus.
Chromosome is a unit or part of the cells in the body that contains various genetic information of humans and passes it on to future generations. However, during the transmission of chromosomes to offspring, errors may occur, such as the 21st chromosome pair in people with Down’s Syndrome having 3 chromosomes instead of the usual 2. Generally, amniocentesis is performed to extract amniotic fluid containing fetal skin cells for analysis to detect chromosomal abnormalities. This is usually done between 16-18 weeks of pregnancy, with results available 2-3 weeks later. Doctors perform amniocentesis on pregnant women who are at risk of having a fetus with genetic abnormalities as follows:
- Pregnant women aged 35 years or older
- History of giving birth to a child with genetic abnormalities
- History of giving birth to a child with Down syndrome due to chromosomal abnormalities
- Previously gave birth to a child with congenital disabilities
- Exposure to radiation or harmful chemicals at the beginning of pregnancy that may cause genetic abnormalities
The risk of having a child with Down syndrome (Trisomy 21) increases with the mother’s age. For example, in the general population, it occurs in about 1:1,000 live births.
- Mothers over 35 years old: about 1:365
- Mothers aged 39 years: about 1:139
- Mothers aged 45 years: about 1:32
Results from Amniocentesis
In addition to detecting chromosomal abnormalities, it also reveals the sex of the fetus and can measure the amount of Alphafetoprotein. If the level is abnormally high, it may indicate abnormalities in the fetal spinal cord and brain.
From Amniocentesis
Complications are very rare, less than 0.5%, depending on the skill and experience of the doctor. Possible complications include infection and amniotic fluid leakage (which, if excessive, may cause miscarriage). Therefore, after amniocentesis, if there are abnormal symptoms such as vaginal bleeding, water breaking, fever, or mild lower abdominal pain, see a doctor immediately. Abnormal symptoms that require medical attention include:
- Fever over 38.5 degrees Celsius
- Severe headache that does not subside
- Blurred or unclear vision
- Severe swelling of feet and ankles
- Painful or burning urination
- Severe and prolonged abdominal pain
- Fetal movement is absent or less than 3 times per hour after 28 weeks of pregnancy
- Vaginal bleeding or significant leakage of amniotic fluid from the vagina
