Pregnancy Testing

 

 

Pregnancy Testing

Birth defects affect 3-4% of all pregnancies. Some, but not all, of the possible birth defects can be discovered by blood tests, ultrasound and genetic testing.

The testing that you decide to perform for your pregnancy is an individual choice based on many factors such as your health, age, previous pregnancy experiences, family’s health history and the number of fetuses you carry.

There are two types of testing for your pregnancy: screening/non-invasive and invasive testing.

Screening tests have no risk to the fetus or the mother. Screening tests include blood tests and ultrasound. Screening tests can identify a women who is at higher risk than expected of having a baby with a birth defect, but cannot detect all of these birth defects (such as spinal cord defects or heart problems).

First trimester (11-13 weeks) screening tests includes a blood test combined with an ultrasound. This testing can detect up to 85% of Down’s syndrome and up to 98% of Trisomy13, Trisomy 18 and Turner’s syndrome. This test is performed at another doctor’s office.

For women over 35 or with a personal or family history of chromosomal defects a blood test is available at 10-18 weeks which identifies more than 99% of fetuses with the four most common genetic defects: Down’s, Trisomy 13, 18 and Turner’s syndrome.

Second trimester (15-20 weeks) screening blood test called a MSAFP is done at 15 weeks in our office. This test predicts fetal risk for spinal cord defects (neural tube defects), Down’s syndrome and Trisomy 18.

At 18-20 weeks an ultrasound will confirm your baby’s growth, your due date and can detect 35% of fetal birth defects, but misses 65% of all birth defects.

Invasive Testing

Invasive tests have a very small risk to the fetus and an extremely rare risk to the mother. Invasive tests include chorionic villous testing and amniocentesis. Invasive tests can diagnose chromosomal birth defects in the fetus (such as Down’s syndrome).

First trimester invasive testing is called a chorionic villous sampling (CVS). A small catheter is passed through the cervix under ultrasound guidance to obtain a small sample of the placenta which contains the baby’s chromosomes. Results in 7-10 days. Risk of miscarriage is 1 in 200.

Second trimester invasive testing is called an amniocentesis. This test is performed by inserting a needle through the mother’s abdomen into the uterine cavity to obtain fetal cells.

Results in 7-10 days. Risk of miscarriage is 1 in 250.

We can refer you to a genetic counselor for more information on invasive testing if needed.

All testing is optional and is your personal choice.