What do antenatal blood tests test for

Testing is available for other genetic defects and disorders depending on your family history and the availability of lab testing at the time of the procedure. An amniocentesis is generally offered to women between the 15th and 20th week of pregnancy who have an increased risk of chromosomal abnormalities. Candidates include women who will be over age 35 at the time of delivery or those who have had an abnormal maternal serum screening test.

An amniocentesis involves inserting a long, thin needle through your abdomen into the amniotic sac to withdraw a small sample of amniotic fluid. The amniotic fluid contains cells shed by the fetus, which contain genetic information.

Although specific details of each procedure may vary, a typical amniocentesis follows this process:. Your doctor will use ultrasound technology to help guide a hollow needle into the amniotic sac. He or she will withdraw a small sample of fluid for lab analysis. You may feel some cramping during or after the amniocentesis. Strenuous activities should be avoided for 24 hours following the procedure.

Women who are pregnant with twins or other higher-order multiples need sampling from each amniotic sac to study each baby. The fluid is then sent to a genetics lab so that the cells can grow and be analyzed. AFP is also measured to rule out an open neural tube defect. Results are usually available in about 10 days to two weeks, depending on the lab.

CVS is a prenatal test that involves taking a sample of some of the placental tissue. This tissue contains the same genetic material as the fetus and can be tested for chromosomal abnormalities and some other genetic problems.

Testing is available for other genetic defects and disorders, depending on your family history and the availability of lab testing at the time of the procedure. Unlike amniocentesis, CVS does not provide information on open neural tube defects. Therefore, women who undergo CVS also need a follow-up blood test between 16 and 18 weeks of pregnancy to screen for these defects. CVS may be offered to women with an increased risk of chromosomal abnormalities or who have a family history of a genetic defect that is testable from the placental tissue.

CVS is usually performed between the 10th and 13th week of pregnancy. Although exact methods may vary, the procedure involves the following steps:. Your doctor may also choose to perform a transabdominal CVS, which involves inserting a needle through your abdomen and into your uterus to sample the placental cells.

You may feel some cramping during and after either type of CVS procedure. The tissue samples are sent to a genetic lab for growth and analysis. Women with twins or other higher-order multiples usually need sampling from each placenta. However, because of the complexity of the procedure and the positioning of the placentas, CVS is not always feasible or successful with multiples.

Women who are not candidates for CVS or who did not get accurate results from the procedure may require a follow-up amniocentesis. An active vaginal infection, such as herpes or gonorrhea , will prohibit the procedure. In other cases, the doctor may take a sample that does not have enough tissue to grow in the lab, generating incomplete or inconclusive results.

During late pregnancy and labor, your doctor may want to monitor the fetal heart rate and other functions. Fetal heart rate monitoring is a method of checking the rate and rhythm of the fetal heartbeat. The average fetal heart rate is between and beats per minute. This rate may change as the fetus responds to conditions in the uterus.

An abnormal fetal heart rate or pattern may mean that the fetus is not getting enough oxygen or indicate other problems. An abnormal pattern also may mean that an emergency cesarean delivery is needed. Using a fetoscope a type of stethoscope to listen to the fetal heartbeat is the most basic type of fetal heart rate monitoring. Another type of monitoring is performed with a hand-held Doppler device. This is often used during prenatal visits to count the fetal heart rate.

During labor, continuous electronic fetal monitoring is often used. Although the specific details of each procedure may vary, standard electronic fetal monitoring follows this process:. The ultrasound transducer is attached to your abdomen with straps so it can transmit the fetal heartbeat to a recorder.

The fetal heart rate is displayed on a screen and printed onto special paper. During contractions, an external tocodynamometer a monitoring device that is placed over the top of the uterus with a belt can record the pattern of contractions. On occasion, internal fetal monitoring is needed to provide a more accurate reading of the fetal heart rate. Your bag of waters amniotic fluid must be broken and your cervix must be partially dilated to use internal monitoring.

Risk factors include. When done during pregnancy, screening tests assess the risk that the fetus has certain common birth defects. A screening test cannot tell whether the fetus actually has a birth defect. There is no risk to the fetus from screening tests. Diagnostic tests can detect many, but not all, birth defects caused by defects in a gene or chromosomes. Diagnostic testing may be done instead of screening if a couple has a family history of a birth defect, belongs to a certain ethnic group, or already has a child with a birth defect.

Diagnostic tests also are available as a first choice for all pregnant women, including those who do not have risk factors. Some diagnostic tests carry risks, including a small risk of pregnancy loss.

No, screening and testing are a personal choice. Some couples would rather not know if they are at risk of having a child with a birth defect or whether their child will have a birth defect. Others want to know in advance.

Knowing beforehand allows the option of deciding not to continue the pregnancy. If you choose to continue the pregnancy, knowing beforehand gives you time to prepare for having a child with a disorder. This means you can organize the medical care your child may need. Talk with your ob-gyn or genetic counselor about your test results.

Anemia : Abnormally low levels of red blood cells in the bloodstream. Most cases are caused by iron deficiency lack of iron. Antibodies : Proteins in the blood that the body makes in reaction to foreign substances, such as bacteria and viruses. Chlamydia : A sexually transmitted infection caused by bacteria. This infection can lead to pelvic inflammatory disease and infertility. Chromosomes : Structures that are located inside each cell in the body. Complications : Diseases or conditions that happen as a result of another disease or condition.

An example is pneumonia that occurs as a result of the flu. A complication also can occur as a result of a condition, such as pregnancy. An example of a pregnancy complication is preterm labor. Diabetes Mellitus : A condition in which the levels of sugar in the blood are too high. Fetus : The stage of human development beyond 8 completed weeks after fertilization. The gene is the basic unit of heredity and can be passed from parent to child.

Genetic Counselor : A health care professional with special training in genetics who can provide expert advice about genetic disorders and prenatal testing. Gonorrhea : A sexually transmitted infection that can lead to pelvic inflammatory disease, infertility, and arthritis. Group B Streptococcus GBS : A type of bacteria that many people carry normally and can be passed to the fetus at the time of delivery.

GBS can cause serious infection in some newborns. Antibiotics are given during labor to women who carry the bacteria to prevent newborn infection. Hepatitis B : An infection caused by a virus that can be spread through blood, semen, or other body fluid infected with the virus. Hepatitis C : An infection caused by a virus that can be spread through infected blood. Intravenous IV Line : A tube inserted into a vein and used to deliver medication or fluids. The shot contains live viruses that have been changed to not cause disease.

The shot is not recommended for pregnant women. Preeclampsia : A disorder that can occur during pregnancy or after childbirth in which there is high blood pressure and other signs of organ injury.

These signs include an abnormal amount of protein in the urine, a low number of platelets, abnormal kidney or liver function, pain over the upper abdomen, fluid in the lungs, or a severe headache or changes in vision.

Rubella : A virus that can be passed to the fetus if a woman becomes infected during pregnancy. You have your blood tested twice more — after one hour and after two hours. If you have gestational diabetes, it means you have a high-risk pregnancy and need additional care and management. Most women can have healthy pregnancies and babies when gestational diabetes is managed well.

You might be referred to a high-risk pregnancy clinic and diabetes educator for help with managing your diabetes. The test usually involves you urinating into a small jar. Your health professional will tell you exactly what to do and send the sample for testing. Urine tests also look at sugar, blood and protein in your urine. These things can be signs of other medical concerns. Group B streptococci GBS are a type of bacteria that often live in the bowel, vagina and anus.

But if the bacteria pass to your baby during birth, this could cause an infection that might make your baby very sick. It's important to speak with a genetic counselor if your baby is at risk for hereditary conditions.

Remember that tests are offered to you — it's your choice whether to have them. To decide which tests are right for you, talk with your health care provider about why a test is recommended, its risks and benefits, and what the results can — and can't — tell you.

Reviewed by: Armando Fuentes, MD. Larger text size Large text size Regular text size. What Are Prenatal Tests? A blood test will check for things like: your blood type and Rh factor. If your blood is Rh negative and your partner's is Rh positive, you may develop antibodies that prove dangerous to your fetus. This can be prevented through an injection given around the 28th week of pregnancy.

Health care providers now routinely offer to screen for these disorders even when there's no family history. These can include: First trimester screening : This test includes a blood test and an ultrasound exam.