what to expect at third trimester genetic testing

• Genetic Screening

• Start Trimester

• Second Trimester

• Ultrasound

• Amniocentesis

• Chorionic Villus Sampling

• Fetal Monitoring

• Glucose

• Group B Strep Culture

Your health care provider may recommend a variety of screenings, tests and imaging techniques during your pregnancy. These tests are designed to provide information about the health of your baby and may assist you optimize your child's prenatal care and development.

Genetic Screening

Many genetic abnormalities can be diagnosed before birth. Your md or midwife may recommend genetic testing during pregnancy if you or your partner has a family unit history of genetic disorders. You may as well choose to have genetic screening if you have had a fetus or baby with a genetic aberration.

Examples of genetic disorders that can be diagnosed before nascency include:

• Cystic fibrosis

• Duchenne muscular dystrophy

• Hemophilia A

• Polycystic kidney affliction

• Sickle cell illness

• Tay-Sachs illness

• Thalassemia

The following screening methods are bachelor during pregnancy:

• Alpha-fetoprotein (AFP) exam or multiple marking test

• Amniocentesis

• Chorionic villus sampling

• Prison cell-gratuitous fetal Deoxyribonucleic acid testing

• Percutaneous umbilical blood sampling (withdrawing a small sample of the fetal blood from the umbilical cord)

• Ultrasound scan

First Trimester Prenatal Screening Tests

First trimester screening is a combination of fetal ultrasound and maternal blood testing. This screening process can help determine the risk of the fetus having sure birth defects. Screening tests may be used alone or with other tests.

Commencement trimester screening includes:

• Ultrasound for fetal nuchal translucency. Nuchal translucency screening uses an ultrasound to examine the area at the back of the fetal neck for increased fluid or thickening.

• Ultrasound for fetal nasal bone conclusion. The nasal bone may not exist visualized in some babies with certain chromosome abnormalities, such equally Down syndrome. This screen is performed using an ultrasound between 11 and xiii weeks gestation.

• Maternal serum (blood) tests. These blood tests measure 2 substances institute in the claret of all meaning women:

  • Pregnancy-associated plasma protein A. A protein produced by the placenta in early pregnancy. Abnormal levels are associated with an increased risk of chromosomal abnormality.

  • Human chorionic gonadotropin. A hormone produced past the placenta in early on pregnancy. Aberrant levels are associated with an increased risk of chromosomal abnormality.

When used together as first trimester screening tests, nuchal translucency screening and maternal blood tests have a greater ability to determine if the fetus might have a nativity defect, such as Down syndrome (trisomy 21) and trisomy 18.

If the results of these first trimester screening tests are abnormal, genetic counseling is recommended. Additional testing, such every bit chorionic villus sampling, amniocentesis, cell-gratuitous fetal DNA or other ultrasounds, may be needed for an accurate diagnosis.

2nd Trimester Prenatal Screening Tests

Second trimester prenatal screening may include several claret tests chosen multiple markers. These markers provide information about your potential risk of having a baby with certain genetic weather condition or nascency defects. Screening is usually done by taking a sample of your blood between 15 and 20 weeks of pregnancy (16 to 18 weeks is platonic). The multiple markers include:

• AFP screening. As well called maternal serum AFP, this blood examination measures the level of AFP in your claret during pregnancy. AFP is a poly peptide commonly produced by the fetal liver that is present in the fluid surrounding the fetus (amniotic fluid). Information technology crosses the placenta and enters your claret. Abnormal levels of AFP may betoken:

  • A miscalculated due date, as the levels vary throughout pregnancy

  • Defects in the intestinal wall of the fetus

  • Downwardly syndrome or other chromosomal abnormalities

  • Open up neural tube defects, such equally spina bifida

  • Twins (more than ane fetus is producing the poly peptide)

• Estriol. This is a hormone produced by the placenta. It can be measured in maternal blood or urine to be used to determine fetal health.

• Inhibin. This is a hormone produced by the placenta.

• Human chorionic gonadotropin. This is also a hormone produced by the placenta.

Abnormal examination results of AFP and other markers may hateful that additional testing is needed. An ultrasound is used to confirm the milestones of your pregnancy and to check the fetal spine and other body parts for defects. An amniocentesis may be needed for an authentic diagnosis.

Since multiple mark screening is not diagnostic, it is not 100 percentage authentic. It helps determine who in the population should be offered additional testing during pregnancy. Imitation-positive results may bespeak a problem when the fetus is actually healthy. On the other mitt, false-negative results signal a normal result when the fetus actually does have a health problem.

When you have both first and 2d trimester screening tests performed, the ability of the tests to detect an abnormality is greater than using just one screening independently. Most cases of Down syndrome can be detected when both first and 2d trimester screenings are used.

Ultrasound

An ultrasound scan is a diagnostic technique that uses high-frequency sound waves to create an image of the internal organs. A screening ultrasound is sometimes washed during the course of your pregnancy to check normal fetal growth and verify the due date.

When are ultrasounds performed during pregnancy?

Ultrasounds may be washed at various times throughout pregnancy for several reasons:

First Trimester

• To institute the due date (this is the well-nigh accurate way of determining the due appointment)

• To determine the number of fetuses and place placental structures

• To diagnose an ectopic pregnancy or miscarriage

• To examine the uterus and other pelvic anatomy

• To find fetal abnormalities (in some cases)

Midtrimester (likewise called the 18- to xx-calendar week scan)

• To confirm the due date (a due date set in the first trimester is rarely inverse)

• To determine the number of fetuses and examine the placental structures

• To assist in prenatal tests, such every bit an amniocentesis

• To examine the fetal anatomy for abnormalities

• To cheque the corporeality of amniotic fluid

• To examine blood flow patterns

• To observe fetal behavior and action

• To measure the length of the cervix

• To monitor fetal growth

Third Trimester

• To monitor fetal growth

• To check the amount of amniotic fluid

• To conduct the biophysical contour exam

• To determine the position of the fetus

• To assess the placenta

How is an ultrasound scan performed?

Two types of ultrasounds can be performed during pregnancy:

• Abdominal ultrasound. In an intestinal ultrasound, gel is practical to your abdomen. The ultrasound transducer glides over the gel on the abdomen to create the image.

• Transvaginal ultrasound. In a transvaginal ultrasound, a smaller ultrasound transducer is inserted into your vagina and rests confronting the back of the vagina to create an image. A transvaginal ultrasound produces a sharper paradigm than an abdominal ultrasound and is often used in early pregnancy.

Which ultrasound imaging techniques are available?

There are several types of ultrasound imaging techniques. As the most common type, the 2-D ultrasound provides a flat picture of one aspect of the baby.

If more information is needed, a 3-D ultrasound test can be done. This technique, which provides a iii-D picture, requires a special machine and special grooming. The 3-D image allows the wellness care provider to come across the width, height and depth of the images, which can exist helpful during the diagnosis. The 3-D images can also be captured and saved for later review.

The latest technology is 4-D ultrasound, which allows the wellness intendance provider to visualize the unborn baby moving in real fourth dimension. With 4-D imaging, a iii-dimensional image is continuously updated, providing a "live activity" view. These images frequently have a golden colour, which helps show shadows and highlights.

Ultrasound images may be captured in withal photographs or on video to document findings.

What are the risks and benefits of ultrasound imaging?

Fetal ultrasound has no known risks other than mild discomfort due to pressure from the transducer on your abdomen or in your vagina. No radiation is used during the procedure.

Transvaginal ultrasound requires roofing the ultrasound transducer in a plastic or latex sheath, which may crusade a reaction in women with a latex allergy.

Ultrasound imaging is constantly being improved and refined. As with any examination, the results may non exist completely accurate. Yet, an ultrasound can provide valuable information to parents and health care providers, helping them manage and care for the pregnancy and the babe. In improver, ultrasound imaging gives parents a unique opportunity to see their baby before birth, helping them to bond and constitute an early human relationship.

Fetal ultrasound is sometimes offered in nonmedical settings to provide keepsake images or videos for parents. While the ultrasound procedure itself is considered safe, it is possible that untrained personnel may miss an abnormality or give parents false assurances nigh their baby'southward well-being. It is best to have an ultrasound performed by trained medical personnel who can correctly translate the results. Talk with your md or midwife if you accept questions.

Amniocentesis

An amniocentesis involves taking a modest sample of the amniotic fluid that surrounds the fetus. It is used to diagnose chromosomal disorders and open neural tube defects, such as spina bifida. Testing is available for other genetic defects and disorders depending on your family history and the availability of lab testing at the fourth dimension of the procedure.

Who is an ideal candidate for amniocentesis?

An amniocentesis is generally offered to women between the 15th and 20th week of pregnancy who have an increased take chances 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 exam.

How is an amniocentesis performed?

An amniocentesis involves inserting a long, sparse needle through your abdomen into the amniotic sac to withdraw a small sample of amniotic fluid. The amniotic fluid contains cells shed past the fetus, which contain genetic information. Although specific details of each procedure may vary, a typical amniocentesis follows this process:

• Your abdomen will be cleansed with an clarified.

• Your doctor may or may not give a local anesthetic to numb the skin.

• Your physician volition utilise ultrasound technology to help guide a hollow needle into the amniotic sac. He or she volition 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 demand sampling from each amniotic sac to study each baby. Depending on the position of the infant and placenta, amount of fluid, and woman's anatomy, sometimes the amniocentesis cannot exist washed. 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 virtually 10 days to two weeks, depending on the lab.

Chorionic Villus Sampling (CVS)?

CVS is a prenatal examination that involves taking a sample of some of the placental tissue. This tissue contains the same genetic material as the fetus and tin can be tested for chromosomal abnormalities and another genetic bug. Testing is available for other genetic defects and disorders, depending on your family history and the availability of lab testing at the fourth dimension of the procedure. Unlike amniocentesis, CVS does not provide information on open neural tube defects. Therefore, women who undergo CVS also need a follow-upward blood test between 16 and eighteen weeks of pregnancy to screen for these defects.

How is CVS performed?

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 ordinarily performed between the 10th and 13th week of pregnancy. Although exact methods may vary, the procedure involves the following steps:

• Your dr. volition insert a small tube (catheter) through your vagina and into your cervix.

• Using ultrasound technology, your doctor will guide the catheter into identify most the placenta.

• Your doctor will remove some tissue using a syringe on the other cease of the catheter.

Your physician may likewise choose to perform a transabdominal CVS, which involves inserting a needle through your abdomen and into your uterus to sample the placental cells. Yous may feel some cramping during and after either type of CVS process. The tissue samples are sent to a genetic lab for growth and analysis. Results are usually available in nearly 10 days to 2 weeks, depending on the lab.

What if CVS is not possible?

Women with twins or other higher-order multiples usually need sampling from each placenta. Yet, because of the complexity of the process and the positioning of the placentas, CVS is not always feasible or successful with multiples.

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

Fetal Monitoring

During tardily pregnancy and labor, your doctor may want to monitor the fetal heart charge per unit and other functions. Fetal heart rate monitoring is a method of checking the charge per unit and rhythm of the fetal heartbeat. The boilerplate fetal heart rate is betwixt 120 and 160 beats per infinitesimal. This rate may modify 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 blueprint also may mean that an emergency cesarean delivery is needed.

How is fetal monitoring performed?

Using a fetoscope (a blazon of stethoscope) to listen to the fetal heartbeat is the nigh basic blazon of fetal eye rate monitoring. Another blazon of monitoring is performed with a manus-held Doppler device. This is frequently used during prenatal visits to count the fetal heart charge per unit. 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:

• Gel is applied to your abdomen to act every bit a medium for the ultrasound transducer.

• 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 chugalug) can record the pattern of contractions.

When is internal fetal monitoring needed?

On occasion, internal fetal monitoring is needed to provide a more accurate reading of the fetal heart rate. Your handbag of waters (amniotic fluid) must be broken and your cervix must be partially dilated to utilize internal monitoring. Internal fetal monitoring involves inserting an electrode through the dilated cervix and attaching the electrode to the scalp of the fetus.

Glucose Testing

Glucose testing is used to measure the level of carbohydrate in your blood.

A glucose challenge test is ordinarily conducted between 24 and 28 weeks of pregnancy. Aberrant glucose levels may betoken gestational diabetes.

What is involved in a glucose challenge exam?

The initial one-hour examination is a glucose claiming test. If the results are abnormal, a glucose tolerance test is needed.

How is a glucose tolerance test performed?

Y'all may be asked to only drink h2o on the twenty-four hours the glucose tolerance test is given. Although the specific details of each procedure may vary, a typical glucose tolerance test includes the following steps:

• An initial fasting sample of blood volition exist fatigued from your vein.

• You will exist given a special glucose solution to drink.

• Blood will be drawn at various times over the course of several hours to measure the glucose levels in your body.

Grouping B Strep Culture

Grouping B streptococcus (GBS) is a type of leaner constitute in the lower genital tract of almost 20 percent of all women. While a GBS infection does not usually crusade bug in women earlier pregnancy, it can crusade serious affliction in mothers during pregnancy. GBS may cause chorioamnionitis (a astringent infection of the placental tissues) and postpartum infection. Urinary tract infections caused by GBS can lead to preterm labor and birth or pyelonephritis and sepsis.

GBS is the most common crusade of life-threatening infections in newborns, including pneumonia and meningitis. Newborn babies contract the infection during pregnancy or from the female parent's genital tract during labor and commitment.

The Centers for Disease Control and Prevention recommends screening all pregnant women for vaginal and rectal GBS colonization between 35 and 37 weeks gestation. The treatment of mothers with sure risk factors or positive cultures is important to reduce the risk of transmission of GBS to the baby. Babies whose mothers receive antibiotic treatment for a positive GBS examination are 20 times less probable to develop the illness than those without handling.

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Source: https://www.hopkinsmedicine.org/health/wellness-and-prevention/common-tests-during-pregnancy

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