10 Weeks – Chromosome Blood Test and Why It Is Only Given at 35+

This week, Frog is about the size of a date.

Prenatal Blood Testing

About mid-week this week is the basic blood work and then the tests that you have the ability to opt out of. The one that most mothers of all ages request is the test that determines gender. One of the primary companies that offers this test is Progenity. The tests gives gender results about 10 weeks earlier than an ultrasound.

The optional tests that are currently offered are:

  • Carrier testing for inherited genetic diseases (such as cystic fibrosis, sickle cell, thalassemia, and Tay-Sachs disease)
  • Chromosome testing for Down’s Syndrome and other chromosome abnormalities, which is the one that also determines gender.

The chromosome test is about 98% accurate, which isn’t 100%. However, it’s less invasive and safer for the baby than the alternative, which is amnio. The test is also known as NIPT or Non Invasive Prenatal Testing.

The test for gender was not thrown in for fun or novelty. Part of the screening includes abnormalities in the X and Y chromosomes, so gender is determined by accident. It’s a nice perk though.

Testing is almost exclusively only available to expectant mother’s of “advanced maternal age.” ( What horrible terminology! It makes you feel like you’re about to check into a nursing home, right?) This unfortunate term means mothers who are age 35 or over.


But, why isn’t the test available to all  expectant mothers?  

Because of the higher occurrence of chromosome defects in older mothers, the test was actually designed specifically for the over 35 age group and it was the only age group that had any real clinical testing before it was offered to the public. Because of this, trials hadn’t  really been performed on younger women when the test was approved for public use.

Some offices tried it with younger mothers after the test came out and they discovered that the test was bringing back a much higher number of inaccurate results than what it was in older patients. Essentially, it just wasn’t made for younger patients and it doesn’t work as accurately. Plus the majority of insurances won’t cover it for the under 35 age group and it’s a pretty expensive test.

The secondary reason is because of the increased tendency for genetic issues in women over 35, it’s a viable replacement for amniocentesis and is a much safer option. Amnio runs the risk of causing a miscarriage. It’s a small risk, but still a risk. The blood chromosome takes your blood from your arm, just like your regular blood test and can be taken at the same time as the routine blood test. It’s one to two extra little vials.

Further information about the Progenity test, it’s costs, and details of testing are in our Week 15 article.

As desire and need for the test increases, other companies are starting to offer the test and hopefully some of the costs will come down. But, in the meantime, few (if any) insurances will cover the test for a patient under 35. Many won’t cover it at all, regardless of the age of the patient.


My “This Week’s Symptoms”

  • Difficulty sleeping
  • Increased nausea
  • Mild breast tenderness
  • Occasional fatigue
  • Cravings for Mac and Cheese


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