Harvard University Health Services

3a. Prenatal Screening Tests

ALPHA-FETOPROTEIN (AFP)
  • This is a blood test done between 16 and 18 weeks gestation. It is a screening test used to detect increased risk for neural tube defects and Down’s syndrome. We will discuss this screening option further during your initial visit
AMNIOCENTESIS
  • This is a diagnostic test offered to women over 35 or with a family history of genetic abnormalities. A sample of amniotic fluid is obtained by passing a thin needle through the mother’s abdomen into the uterus. Cells from this fluid are grown in a genetic lab for 2 weeks. The chromosomes are then studied for Down Syndrome and other chromosomal abnormalities. Genetic counseling is provided at the time of the amniocentesis and again in more detail should an abnormality be detected.
FETAL MOVEMENT ( KICK COUNT)
  • Your baby has a sleep- wake cycle lasting from 20 minutes to 2 hours. This and other factors influence the mother’s ability to feel her baby move. The first “flutter” is usually felt between 16 and 20 weeks of pregnancy. Fetal movement is more perceptible in mid pregnancy and may diminish as the pregnancy progresses to term. Kick count refers to spontaneous fetal movements experienced by the mother. There is no universal consensus on a critical level of fetal movement. However, if you are concerned that the baby’s activity has diminished from its previous pattern of movement, please notify us.

GLUCOSE LOADING TEST (GLT)
  • This is a blood test performed one hour after taking a flavored glucose drink. It is a screening test for diabetes, which sometimes arises during pregnancy. It is usually performed at 26-28 weeks

HIV TESTING
  • It is recommended that all pregnant women have a test for HIV. You will be asked about previous testing and your permission to have an HIV test. You will need to sign a consent form, which will be part of your permanent medical record.

NON-STRESS TEST (NST) /BIOPHYSICAL PROFILE (BPP)
  • These tests assess fetal and placental well-being. The NST follows the baby’s heartbeat with an external monitor for about 30 minutes. The BPP uses ultrasound to observe fetal activity, fetal muscle tone, fetal breathing and amniotic fluid volume. They are performed in certain circumstances during the third trimester.

RHOGAM
  • At your first prenatal visit, a blood test is performed to determine your blood type. For women who are RH negative, an injection of RHOGAM is given at 28 weeks of pregnancy and again postpartum if your baby is RH positive. These injections prevent contamination of maternal blood with fetal RH+ cells and subsequent antibody formation, which can complicate future pregnancies.

SICKLE CELL DISEASE
  • Infants can be born with Sickle Cell Disease if both parents are carriers of Sickle Cell Trait. The disease is a serious blood condition that can cause episodes of severe pain, anemia, and other serious health problems. Sickle Cell Trait alone rarely causes health problems and is generally unrecognized. A simple blood test can determine whether a person is a carrier of Sickle Cell Trait. When two carriers have a child, the child may have a change of inheriting Sickle Cell Disease.
  • In the U.S., most cases of Sickle Cell Disease occur among Blacks and Hispanics of Caribbean ancestry. These couples are at increased risk and should be tested.

TAY SACHS DISEASE
  • If you and the father of the baby are both Jewish or French Canadian and have never been screened for this genetic disorder, please let us know. A blood test can be performed free of charge and counseling can be arranged.

TB TESTING
  • We ask that any of our patients that are high risk for TB have a TB test in their 16th week. High prevalence countries are Africa, Asia except Japan, Central/South America, Mexico, Eastern Europe, Caribbean, Middle East. If you are from one of these countries and have not been immunized, we recommend a TB test be done. Testing is done on the 3rd floor in the immunization clinic.

THALASSEMIA
  • Infants can be born with Thalassemia (Mediterranean Anemia) if both parents are carriers. Thalassemia includes a number of different forms of anemia; the severe form may result in multiple health problems, anemia, and may require multiple blood transfusions. Thalassemia carriers generally do not have symptoms of anemia, although some may have mild anemia. Carriers of Thalassemia can be detected by a simple blood test.
  • Individuals of Italian or Greek heritage are at highest risk. Others who may be at risk include those of Southeast Asian, Middle Eastern and African ancestry. Women who are at highest risk should be tested.

ULTRASOUND
  • This is a diagnostic test utilizing sound waves to produce an image of the fetus before birth. We may recommend this test for specific indications, e.g. vaginal bleeding, question of twins or to assess fetal growth.

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