Should You Consider Amniocentesis After Maternal Blood Screening?

Maternal blood screening for Down syndrome?

I am 31 years old and currently 17 weeks pregnant.
At 15 weeks, I underwent maternal serum screening, which resulted in a risk of 1 in 431, with an AFP of 42.74, AFP MoM of 1.18, B-HCG of 110.49, and B-HCG MoM of 2.11.
The doctor suggested that I consider amniocentesis, but I have heard from friends that there are risks associated with the procedure, and the doctor mentioned that the accuracy of amniocentesis is only 80%.
Based on my test results, should I consider amniocentesis? Could you please provide your opinion? I am also considering going to another hospital for a blood test; will the results be the same? Should I do this? I plan to have a high-level ultrasound around 20 weeks; will this help confirm the baby's health? Thank you for taking the time to respond!

kitty, 30~39 year old female. Ask Date: 2005/01/24

Dr. Huang Jianxun reply Obstetrics and Gynecology

Maternal blood screening for Down syndrome uses a reference value of 1 in 270.
If the risk exceeds 1 in 270, the physician will recommend further amniocentesis.
The risks associated with amniocentesis include rupture of membranes, infection, and miscarriage, but the probability is only about 1 to 5 in 1000.
With the strict quality control of amniotic fluid laboratories, the amniotic fluid report is equivalent to a definitive conclusion.
Recently, through these steps, we identified a case of Down syndrome, demonstrating that this screening and diagnostic process is meaningful.

Reply Date: 2005/01/24

More Info

Amniocentesis is a prenatal diagnostic procedure that can provide valuable information about the genetic health of a fetus. Given your situation, where you are 31 years old and currently 17 weeks pregnant, it is understandable to have concerns about the risks and benefits of this procedure, especially after receiving your maternal blood screening results.

Your screening results indicate a risk of 1 in 431 for chromosomal abnormalities, which is considered a moderate risk. The levels of Alpha-fetoprotein (AFP) and Beta-human chorionic gonadotropin (B-HCG) you provided suggest that further investigation may be warranted. While the accuracy of amniocentesis is indeed high, it is important to note that it is not 100% foolproof. The procedure carries a small risk of miscarriage, estimated to be around 1 in 300 to 1 in 500, depending on various factors including the skill of the practitioner and the specific circumstances of the pregnancy.

When considering whether to proceed with amniocentesis, it is essential to weigh the potential benefits against the risks. Amniocentesis can provide definitive information about chromosomal conditions such as Down syndrome, trisomy 18, and other genetic disorders. If you have a family history of genetic disorders or if the screening results indicate a higher risk, amniocentesis may be a prudent choice. Additionally, if you are considering options for further management of the pregnancy based on potential findings, this procedure can provide clarity.

Regarding your question about whether to seek a second opinion or undergo additional blood tests at another facility, it is reasonable to do so. Different laboratories may have slightly different reference ranges or methodologies, which could yield varying results. However, it is also important to consider the timing of these tests, as the results from the maternal blood screening are typically most relevant during the first and second trimesters.
As for the high-level ultrasound at 20 weeks, this can indeed provide additional information about the fetal anatomy and help identify any structural abnormalities. While it cannot definitively diagnose chromosomal abnormalities, it can help assess the overall health of the fetus and may provide reassurance.

In summary, the decision to undergo amniocentesis should be made after careful consideration of your individual circumstances, including your risk factors, the potential benefits of obtaining more definitive information, and your comfort level with the associated risks. Consulting with a genetic counselor or a maternal-fetal medicine specialist can also provide you with more personalized guidance based on your specific situation. Ultimately, the goal is to ensure the best possible outcome for both you and your baby.

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