Prenatal Tests

Prenatal testing can detect potential problems and monitor health throughout pregnancy

Our San Antonio OBGYNs work diligently to help you have the safest, healthiest pregnancy possible by providing comprehensive obstetrics care. Prenatal tests are part of this plan. Some forms of prenatal testing may occur at any time during the pregnancy. However, in some cases, the timing of the test is more important. For example, our team may perform an early ultrasound in the first trimester. However, it is more common for women to have an ultrasound during the second trimester.

First trimester prenatal tests

On your first prenatal visit to our San Antonio OBGYNs, you will have several routine prenatal tests, such as a complete blood count (CBC), a urine culture and a urinalysis. We also test to see if you have been vaccinated for rubella and determine whether you have any sexually transmitted infections (STIs). We give these routine prenatal tests to every pregnant woman.

Screening tests are prenatal tests that can detect problems with the baby, primarily genetic conditions. Discuss your need for these tests with our San Antonio OBGYNs.

First-trimester screening. Between the 11th and 13th week of pregnancy, an ultrasound and bloodwork can determine whether your baby is at risk for chromosomal disorders.

Chorionic villus sampling (CVS). This prenatal test, conducted between weeks 10 and 12, involves taking and examining a small tissue sample from the placenta to determine whether the baby is at risk for chromosomal disorders, such as Down syndrome.

Carrier screening. These tests can be done during pregnancy or before you get pregnant. It determines whether you or your partner is a carrier of the genes for specific disorders such as cystic fibrosis.

Second trimester prenatal testing

During the second trimester, during weeks 26 to 28, our OBGYNs recommend having a glucose challenge screening to determine whether you have, or are at risk for, having gestational diabetes.

Women who have high risk factors for having a child with a disorder, such as Down syndrome or spina bifida, may consider having amniocentesis during weeks 15 to 20.

Third trimester prenatal tests

Our San Antonio OBGYNs routinely perform two prenatal tests in the third trimester.

  • Group B streptococcus test. At 36 to 37 weeks, this test looks for the bacteria that causes this infection.
  • Rh antibodies test. Between weeks 28 and 29, if you are Rh negative, you will need a blood test to test for Rh antibodies.

Prenatal tests are an important component of good prenatal care

The mission of our San Antonio OBGYNs is here to provide every patient with the best pregnancy they can possibly have. Contact us to learn more about preventive care and prenatal tests.