Prenatal testing

Tests done early in pregnancy

Several tests have been developed in recent years that provide information about fetal health and development. Most of these tests will be provided in the comfort and convenience of your health care provider's office. Discuss these tests with your doctor or midwife.

Chorionic villus sampling (CVS)
The CVS test offers women earlier testing than ever before possible. The test is done at 10 to 11 weeks of pregnancy. A small amount of placenta is withdrawn, either with a needle placed through the skin or with a thin tube passed through the cervix. It may be a good choice for women who are at high risk or those who want their results sooner. Although the risks associated with a CVS are not high, it does carry a higher rate of miscarriage than amniocentesis. It can occasionally give results difficult to interpret.

Alpha Fetoprotein (AFP)
This blood test is done between the 15th and 18th week of pregnancy and is used to detect spina bifida and other abnormalities in the fetus and to evaluate the risk of Down syndrome in women under 35. High AFP levels may signal neurological defects; low levels may indicate Down syndrome. Genetic consultation at Yale-New Haven or further testing--an ultrasound or maybe amniocentesis--may be offered.

Triple Screen
This blood test checks for AFP, human chorionic gonadotropin (hCG and unconjugated estriol, two hormones released when you become pregnant). Triple screen helps identify risk of Down syndrome.

Ultrasound
Ultrasound, a diagnostic imaging procedure using sound waves, can be used throughout pregnancy to assess and monitor fetal age and growth and help diagnose abnormalities in the fetus and mother's pelvis. Sometimes ultrasound can be used to check the gender of the baby. While most babies are normal, ultrasound can be used to detect certain physical problems that can be treated before the fetus is born with the assistance of Yale's Fetal Therapy program.

Or, if you deliver at Yale-New Haven, physicians can be available to treat the problem shortly after birth, if necessary. Transvaginal ultrasound can be done very early in pregnancy to rule out ectopic pregnancy or monitor fetal progress.

Amniocentesis
Amniocentesis is generally performed as early as 15 weeks of pregnancy. Early in pregnancy it is used to detect chromosomal problems, including Down syndrome, neural tube defects (spina bifida) and occasionally other genetic diseases. Later in pregnancy it may be used to rule out an infection or to test for fetal lung maturity. Amniocentesis does not detect all birth defects or problems like sickle cell anemia or diabetes. During amniocentesis, a small amount of amniotic fluid is removed from the amniotic sac surrounding the fetus. A needle is inserted through the abdomen into the uterus and amniotic sac. Results are usually available in seven to 10 days.

Genetic consultation by a trained and certified Yale-New Haven counselor can help you make make the decision whether to have amniocentesis and how to interpret the results. For information, call (203) 785-2661.

PUBS (Percutaneous Umbilical Blood Sampling)
PUBS is the insertion of a needle through the mother's abdomen, like an amniocentesis, to take a blood sample from the umbilical vein of the umbilical cord. This is usually done to get fetal blood for a quick chromosome analysis or to check if the baby is anemic. A blood transfusion can be done while the needle is in place.

Continue: Tests done later in pregnancy

Additional resources:
Yale High Risk Obstetrics Prenatal Testing and Diagnosis

How to make an appointment for prenatal testing at Yale-New Haven

Maternity Services home page

Last revised: July 19, 2005 (jj)

Home page URL: http://www.ynhh.org

All information is intended for your general knowledge and is not a substitute for medical advice or treatment for specific medical conditions. You should seek prompt medical care for any specific health issues and consult your physician before starting a new fitness regimen.