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Amniocentisis or CVS. Essential for women over 35 years old?

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Internal Medicine Specialist
Practicing since : 1998
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I am 41 year old, and this is my first pregnancy. I am 4 months pregnant now, and my OB-GYN has not asked for any tests that would suggest an amniocentisis or CVS...Isn't it normal for all women over 35 to go thru these additional tests for Down's etc?
Posted Thu, 19 Apr 2012 in Pregnancy
Answered by Dr. Jasvinder Singh 32 minutes later

Thanks for posting your query. I can understand your concern for Down’s syndrome because of your age. Amniocentesis is usually done between 15 and 20 weeks gestation. Though all women should be offered the option of having an amniocentesis and CVS but it is primarily done in those who are primarily those at increased risk for genetic and chromosomal problems because the test is invasive and carries a small risk of miscarriage.

I agree that after the age of 35, the risk of Down’s syndrome increases and by age 40, the rate increases to 1 in 63. But the risk of miscarriage is there and moreover it only will identify 15-30% of all cases of Down’s syndrome. Hence maybe your doctor did not get this test done because of this risk. It is done only when the use outweighs the risk.

What can be done at this stage is that you can get a triple test done. Triple test measures the levels of hormones and AFP & hCG, with or without oestriol are usually done. Blood is taken at about 16 weeks or 4 months gestation, and a risk value is calculated. A positive test emphasis that amniocentesis and CVS is mandatory to be done as the next step. Most use the cut-off of 1 in 250 as being positive.

You can talk to your doctor about this test and get it done.

Lastly, the dose of Thyronorm increases in pregnancy and if you are taking thyronorm then you should get the dose monitored by getting the thyroid function tests done at regular intervals.

Hope this answers your query. If you have additional questions or follow up queries then please do not hesitate in writing to us. I will be happy to answer your queries.

Wishing you good health.

Above answer was peer-reviewed by
Follow-up: Amniocentisis or CVS. Essential for women over 35 years old? 1 hour later
Thank you. What you said makes sense...My NT scan (done at 10 weeks 5 days) result showed that the nuchal thickness was 1 mm and they said everything looked normal. Maybe that's why the Doc didn't go for amnio or CVS.

However, my TSH (test was done at about 8 weeks) was 3.65 and the Doc asked me continue with same dosage of 100 mcg. Am not comfortable with this...because in my last pregnancy (had a miscarraige at 12th week) the Doc at that time had asked me to double my dosage only once during the weekend, and same dosage on all other weekdays.

Your comments on this please...
Answered by Dr. Jasvinder Singh 4 hours later

Thanks for writing back.

The NT scan (nuchal thickness scan) is the first test done for Down's syndrome and normal 'nuchal thickness' should be less than 3mm.

"1m nuchal thickness is fine".

If there is any abnormality in the NT scan, then the triple scan is done. If that comes abnormal then amiocentesis and invasive investigations are suggested. In your case, since the NT scan is normal, hence relax as hopefully the triple test will also come out fine.

During pregnancy two hormones are produced; these are hCG and estrogen which cause increased thyroid hormone levels in the blood. The dose of thyroid supplements increase by approximately 50% during the pregnancy and hence the dose needs to be 50% more compared to the non-pregnant adult. I can understand your concern for the thyroid medicine dosage; but one has to keep a close watch on the dosage, which strictly depends on the level of thyroid hormones and TSH levels.

Moreover get regular ante-natal checkups done to rule out or detect early complications of hypothyroidism. These include anemia, low birth weight and pre eclampsia. So get your hemoglobin count, ultrasounds and BP monitored at regular intervals.

Continue with the thyroid medicine after discussion with endocrinologist and keep a watch on above mentioned parameters. Also get the tests repeated every 6-8 weeks to keep an eye on the levels and hence adjust the dose accordingly.

Hope this answers your query. If you have additional questions or follow up queries then please do not hesitate in writing to us. I will be happy to answer your queries.

Wishing you good health
Above answer was peer-reviewed by
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