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Maternal Newborn Nursing

13.2 Prenatal Testing during the Second Trimester

Maternal Newborn Nursing13.2 Prenatal Testing during the Second Trimester

Learning Objectives

By the end of this section, you will be able to:

  • Explain the purpose, results, and nursing care when obstetric ultrasound is performed in the second trimester of pregnancy
  • Explain the purpose, results, and nursing care when maternal assays and multiple marker screenings are performed in the second trimester of pregnancy
  • Explain the purpose, results, and nursing care when prenatal diagnostic tests are performed in the second trimester of pregnancy
  • Explain the purpose, results, and nursing care when antibody titers are performed in the second trimester of pregnancy
  • Explain the purpose, results, and nursing care when fetoscopy is performed in the second trimester of pregnancy
  • Explain the purpose, results, and nursing care when MRI is performed in the second trimester of pregnancy

Second trimester prenatal testing may be routinely offered during pregnancy. It also may be recommended if screenings done in the first trimester came back abnormal. Other reasons for second trimester prenatal testing include:

  • detecting congenital anomalies
  • evaluating the condition of the fetus if the pregnancy is high risk and allow appropriate intervention
  • providing baseline information

Prenatal testing in the second trimester is offered to all pregnant persons regardless of the risk factors present. Nurses have an important role in educating pregnant persons about the prenatal tests that are offered or recommended so that the pregnant person can decide whether to have testing done. Tests available during the second trimester include the following:

  • ultrasound
  • umbilical Doppler study
  • integrated screen part 2 (quad screening)
  • alpha-fetoprotein screening
  • percutaneous blood sampling (PUBS)
  • antibody titer
  • fetoscopy
  • Magnetic resonance imaging (MRI)

The results of the screenings and tests can help pregnant persons and their families make decisions about continuing the pregnancy or preparing for the delivery of an infant who may have special needs or require additional medical care.

Ultrasound

Pregnant persons are offered a second trimester ultrasound exam to look for fetal structural defects. This is a routine screening to primarily assess fetal anatomy, detect any fetal anomalies, and assess the fetal weight. This ultrasound can help determine if any special care or interventions are needed for the remainder of the pregnancy. The second trimester fetal ultrasound scan should be performed between 18 and 22 weeks of gestation (ACOG, 2023).

An ultrasound technician will usually perform this test in the clinic. A two-dimensional grayscale abdominal ultrasound is routinely used to evaluate the fetal number, viability, gestational age, anatomic survey, placenta location, amniotic fluid, and maternal pelvic organs (Jabaz & Abed, 2023) (Figure 13.4).

Ultrasound image of fetus in utero during the second trimester.
Figure 13.4 Second Trimester Ultrasound This is a common view expectant parents will have printed that shows the fetus’s profile. The nasal bone, nose, mandible, and hard palate are visible. (credit: “Early second trimester ultrasound” by Robyn Alvarez/Flickr, CC BY 4.0)

The nurse has an important role in preparing the pregnant person for this screening. The nurse must validate and document the last menstrual cycle to determine that the ultrasound is completed during the appropriate time frame. The pregnant person should be instructed to arrive with a full bladder. This allows for better imaging of the lower uterine segment. The nurse informs the pregnant person that a semi-recumbent position is the most commonly used position for this screening. The pregnant person will be asked to lie on a padded table with a pillow during the procedure. The head of the bed can be slightly elevated. The ultrasound technician will instruct the pregnant person on the correct positioning for the screening (Jabaz & Abed, 2023).

The ultrasound technician will take pictures of the fetal skull and brain, face and neck, thorax, abdomen, spine, extremities, and external genitalia. The placenta and amniotic fluid volume will also be assessed and measured during this screening. Pictures of the fetus can be printed for the pregnant person if desired. The pregnant person should tell the ultrasound technician if they do or do not want to know the sex of the fetus. During the screening, the pregnant person and their support person will be able to see the fetus moving and see the heart beating (Jabaz & Abed, 2023). Other indications for a second trimester ultrasound include the following:

  • screening for fetal anomalies
  • evaluating fetal anatomy
  • evaluating fetal growth
  • evaluating vaginal bleeding
  • evaluating abdominal or pelvic pain
  • checking for cervical insufficiency
  • checking for suspected multiple gestation
  • evaluating significant discrepancy between uterine size and clinical dates
  • evaluating pelvic mass
  • evaluating suspected hydatidiform mole
  • evaluating suspected fetal death
  • checking fetal well-being
  • performing umbilical Doppler flow studies
  • evaluating suspected amniotic fluid abnormalities
  • evaluating suspected placental abruption
  • evaluating premature rupture of membranes or premature labor
  • evaluating abnormal biochemical markers
  • evaluating fetal condition in later registrants for prenatal care
  • estimating gestational age
  • determining fetal presentation
  • guiding procedures like amniocentesis, cervical cerclage placement, or external cephalic version
  • following up on fetal anomaly
  • following up on placental location for suspected placenta previa
  • if history of previous congenital anomaly is present
  • assessing for findings that may increase the risk for aneuploidy

Umbilical Doppler Studies

An umbilical Doppler study (Figure 13.5) is used to check the blood flow in the umbilical arteries, which are blood vessels located in the umbilical cord. The Doppler ultrasound is used with other tests when the fetus shows signs of not growing well (ACOG, 2019a). This study can be performed as early as 22 weeks’ gestation and is performed during the second and third trimesters (Adekanmi, et al, 2022). The umbilical Doppler study is recommended if the pregnant person has one or more of the following pregnancy-related or preexisting conditions (Maulik, 2022):

  • suspected fetal growth restriction (FGR)
  • previous pregnancy with FGR or fetal death in utero
  • decreased fetal movement
  • oligohydramnios
  • polyhydramnios
  • multifetal pregnancy
  • twin-twin transfusion syndrome
  • twin anemia-polycythemia sequence
  • gestational diabetes or preexisting diabetes mellitus
  • pregnancy-induced hypertension (PIH), pre-eclampsia, or chronic hypertension
  • renal disease
Image of fetus in utero with umbilical arteries indicated in the color purple.
Figure 13.5 Umbilical Doppler Study When an umbilical Doppler study is performed, the ultrasonographer locates the umbilical cord and follows the blood flow through the umbilical arteries (purple). (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

For this procedure, the nurse will need to educate the pregnant person on what to expect before, during, and after the umbilical Doppler study. The pregnant person will be in a reclined or lying-down position during this test. An ultrasound transducer is gently rolled over the abdomen to project sound waves. An image of the artery being examined is viewed on the computer screen (ACOG, 2019a).

A normal test result shows normal blood flow in the umbilical artery. If the test shows a problem with the blood flow in the umbilical artery, it could mean that insufficient oxygen is being delivered to the fetus (ACOG, 2019a). When abnormal results are obtained, it is recommended to have a further sonographic workup to test the degree of placental insufficiency with a fetal midcerebral arterial Doppler assessment, a ductus venous flow assessment, or an umbilical venous flow assessment (Murphy, 2023).

Maternal Assay and Multiple Marker Screening in the Second Trimester

Several blood tests are recommended in the second trimester of pregnancy, which are known as multiple marker screenings. These tests provide information about the patient’s risk of having a fetus with certain genetic conditions or abnormalities.

Integrated Screen Part 2 (Quad Screen)

The integrated screen part 2, or quad screen, is a blood test taken between 15 and 20 weeks’ gestation to screen for neural tube defects such as spina bifida and chromosomal disorders such as Down syndrome and trisomy 18. The integrated screen part 2 is performed as the quad screen when first trimester screening has not been performed. When the results of the first trimester integrated screen part 1 are combined with the integrated screen part 2, the results are more accurate (Nguyen, 2022).

If a patient’s first integrated screen test result showed low risk, the pregnant person will return for the integrated screen part 2. The second blood test measures the following:

  • Maternal serum alpha-fetoprotein (AFP): secreted by the liver of the fetus and then passed into the pregnant person’s blood. Levels that are too high or too low have been associated with birth defects (Fuentes, 2018).
  • Estriol (uE3): highest amount of circulating hormone in a pregnant person. Low levels of estriol are associated with an increased risk for Down syndrome and trisomy 18 (Fuentes, 2018).
  • Human chorionic gonadotropin (hCG): known as the pregnancy hormone. During the second trimester, the pregnant person produces less of this hormone than in the first trimester. High levels of hCG are associated with Down syndrome; however, there can be other reasons, like multiple gestation, for this hormone to be elevated. Low levels of hCG hormone in the second trimester are associated with trisomy 18 (Fuentes, 2018).
  • Inhibin-A: hormone produced by the placenta (and ovaries). Adding inhibin A to the screening improves the accuracy of the multiple marker screen for identifying trisomy 21 in patients younger than age 35 (Fuentes, 2018).

A positive result means that the developing fetus is at a higher risk for having Down syndrome, trisomy 18, or an open neural tube defect. A positive result does not mean the fetus will have these problems, but they have a higher risk. As a result, the health-care provider may recommend additional testing, such as a detailed fetus anatomy ultrasound or amniocentesis (Palka et al., 2019).

Alpha-Fetoprotein (AFP) in the Second Trimester

The alpha-fetoprotein (AFP) test (by itself) is a blood test that measures the level of alpha-fetoprotein in the pregnant person’s blood to look for a risk of fetal neural tube abnormalities. AFP is dispersed from fetal plasma into fetal urine and excreted into the amniotic sac. This screening can be measured from maternal serum or from amniotic fluid. The AFP test is considered a screening, not a diagnostic test. An abnormal result does not mean the developing fetus has a neural tube abnormality but suggests a potential disorder risk. This screening may be done with other tests to determine if further diagnostic tests are needed (U.S. National Library of Medicine, 2022c).

The AFP test is usually recommended between the 15th and 22nd weeks of pregnancy. All pregnant persons should be offered AFP screening regardless of risk factors (U.S. National Library of Medicine, 2022c). Patients at higher risk include:

  • persons who have a positive family history of birth defects
  • persons age 35 or older
  • persons who use high-risk medications or drugs while pregnant
  • persons who have diabetes

If the AFP results are normal, there is a low risk of the fetus having a genetic, neural tube defect, or chromosomal abnormality (U.S. National Library of Medicine, 2022c). An abnormal AFP level may mean that the patient’s due date is earlier or later than expected. Inaccurate gestational age is the most common reason for AFP levels being abnormal (Palka et al., 2019). Another reason that AFP levels may be abnormal is if the pregnant person is pregnant with more than one fetus. Each fetus makes AFP, so AFP levels will be higher with two or more fetuses (U.S. National Library of Medicine, 2022c). Conditions that can make the fetus release more or less AFP are summarized in Table 13.3.

Level of Alpha-Fetoprotein Associated Conditions
Elevated
  • open neural tube defects (anencephaly, spina bifida)
  • esophageal obstruction
  • increased amount leaked by fetal kidney (hydronephrosis)
  • abdominal wall defects
  • threatened abortion
  • fetal death
  • amniotic fluid contaminated with fetal blood during amniocentesis
  • underestimation of fetal age
  • multifetal gestation
  • incorrect maternal weight (lower than true weight)
  • maternal insulin-dependent diabetes
Low
  • chromosomal trisomies (Down syndrome)
  • gestational trophoblastic disease
  • overestimation of gestational age
  • incorrect maternal weight (higher than true weight)
Table 13.3 Conditions Associated with Abnormal Maternal Serum Alpha-Fetoprotein Levels

Pregnant persons may choose to pursue AFP testing or not. Testing can provide opportunities for the expecting parents to pursue potential medical interventions that may be available, plan for a child with special needs before the birth, address anticipated lifestyle changes, identify support groups and resources, and make the decision to carry the pregnancy to term or terminate it (U.S. National Library of Medicine, 2022c).

Role of AFP in Screening for Genetic Disorders

If the AFP levels are low and abnormal levels of human chorionic gonadotropin (hCG) and estriol are also found, it may indicate the fetus is at higher risk for trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), or another type of chromosomal abnormality (U.S. National Library of Medicine, 2022c).

If the AFP test comes back abnormal, additional diagnostic testing is recommended. Less invasive diagnostic testing includes:

  • a second AFP test
  • a complete triple-screen test (this test includes testing for AFP, hCG, and estriol)
  • high-definition ultrasound

An amniocentesis may be recommended if the additional testing results are still abnormal. Approximately 20 to 50 abnormal AFP tests result for every 1,000 pregnancy tests. Of those, only 1 in 16 to 1 in 33 results in a fetus with a neural tube defect or other chromosomal abnormality (U.S. National Library of Medicine, 2022c).

Role of AFP in Screening for Neural Tube Defects

Neural tube defects are the most common birth defects in the United States, affecting about 1 in 1,000 births (U.S. National Library of Medicine, 2022c). The AFP screening test is a widely used mass screening technique that successfully screens for birth defects during pregnancy. This test is specifically designed to detect neural tube defects in addition to other structural malformations in the developing fetus. Maternal serum AFP screenings can detect 85 percent of neural tube defects (U.S. National Library of Medicine, 2022c).

The nurse can prepare the pregnant person for this test by educating the patient on what the test is looking for and why it is recommended. If the test result comes back positive, the nurse will need to educate the patient on the result and inform the pregnant person that there is an increased risk of the fetus having one of the listed disorders. It is important to remind the patient that the test is not diagnostic. The nurse provides support to the patient if the results come back positive and assists the provider in scheduling or ordering additional screening and diagnostic tests. Referring the patient to a genetic counselor may also be done (U.S. National Library of Medicine, 2022c).

Prenatal Diagnostic Tests in the Second Trimester

During the second trimester, additional diagnostic testing may be recommended based on the age of the patient or other risk factors a patient might have. These diagnostic tests include an amniocentesis, percutaneous umbilical sampling (PUBS), antibody titer, fetoscopy, and magnetic resonance imaging (MRI).

Amniocentesis in the Second Trimester

An amniocentesis is a medical procedure done during pregnancy that involves removing fluid and cells from the uterus (Figure 13.6). It is a diagnostic test that can tell if the fetus has a specific health problem, and it is very accurate (ACOG, 2021a). Once the sample is taken, it is tested to determine if the fetus has any genetic disorders. This diagnostic test can also check for infection and lung development (ACOG, 2021a).

Image of pregnant person with fetus in utero. A large needle is being inserted into the abdomen, going into the uterus and extracting amniotic fluid. Ultrasound wand is visible on abdomen.
Figure 13.6 Amniocentesis During an amniocentesis, a large-bore needle is inserted under ultrasound guidance into a pocket of amniotic fluid. A syringe is attached to the needle and fluid is withdrawn. (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

An amniocentesis is recommended for pregnant persons who have an increased risk of having a fetus with a birth defect. Common recommendations for a patient to have an amniocentesis include:

  • maternal age 35 years or older
  • chromosomal abnormality in a close family member
  • gender determination for a maternal carrier of X-linked disorder (hemophilia, Duchenne muscular dystrophy)
  • birth of previous infant with a chromosomal abnormality or neural tube or body-wall defect
  • pregnancy after multiple spontaneous abortions
  • elevated levels of maternal serum alpha-fetoprotein that remain unexplained
  • sensitization of maternal Rh-negative blood to fetal Rh-positive blood

The fluid tested is evaluated for missing, damaged, or extra chromosomes, which are signs of genetic disorders. Specific disorders caused by genetic mutations can also be found by doing an amniocentesis. Amniocentesis tests for the following disorders:

  • cystic fibrosis
  • Down syndrome (trisomy 21)
  • sickle cell disease
  • Tay-Sachs disease
  • neural tube defects like spina bifida and anencephaly

An amniocentesis is usually done between 15 and 20 weeks’ gestation but can be performed up until birth. If the results are negative, it means that the fetus does not have the disorder it was tested for. If the results are positive, it means the fetus does have the disorder that it was tested for. The OB/GYN will discuss the results with the pregnant person and will likely refer them to a genetic counselor to help provide guidance about choices and options for the pregnancy. The pregnant person and their partner may want to talk with a specialist in the disorder to understand more about the child’s life expectancy, what treatments are available, and what type of care the child will need after birth. Support groups, counselors, and social workers may also be beneficial for the pregnant person and partner as they prepare for a child with a genetic disorder. They may also want to consider additional testing, like a specialized ultrasound exam (ACOG, 2021c).

While the provider will discuss the risks and benefits of the procedure with the pregnant person while obtaining informed consent, the nurse can help prepare the pregnant person by educating them on what to expect before, during, and after the procedure. The nurse will review the pregnant person’s chart for blood type, Rh, and antibody screen and auscultate the fetal heart rate. The nurse will explain that during the amniocentesis the pregnant person may feel mild stinging, pressure, or cramping. Afterward, the pregnant person may have mild abdominal discomfort or cramping. Communicating with the pregnant person during the procedure and providing emotional support are also part of the nurse’s role.

An amniocentesis is usually performed in an office or medical center. The pregnant person will be asked to lie on their back on an exam table. The provider may apply a numbing medicine to the abdomen (ACOG, 2021a). A needle is inserted into the abdomen and into the uterus. An ultrasound is used to guide the needle into the correct location. Once the needle is inserted into the uterus, a small sample of amniotic fluid is withdrawn from the sac surrounding the fetus. The sample is then sent to the lab for testing. The procedure usually takes about 15 minutes. After the procedure, the nurse will auscultate the fetal heart rate and monitor the pregnant person per policy. The nurse will instruct the pregnant person to avoid any hard exercise or physical activity for the next 24 hours (ACOG, 2021a). The nurse will inform the pregnant person that vaginal spotting or leaking a small amount of amniotic fluid from the vagina may occur. Increased abdominal pain, vaginal bleeding, and fever should be reported to the health-care provider. Results can take 1 day to several weeks to return, depending on what disorders are being tested for (ACOG, 2021a). The risk of serious complications is low. There is less than a 1 percent chance of miscarriage with an amniocentesis (ACOG, 2021a).

Planning ahead for a baby with a genetic disorder can be helpful. This can give the pregnant person and their partner time to learn about the condition and plan for any additional care their child might need. If the disorder is serious and has a short life expectancy, it allows the family to arrange palliative care for the baby right away. Some people may also choose to end the pregnancy. This can bring up many ethical and legal issues, as some conditions are unable to be definitively diagnosed until the second trimester. Many states have abortion restrictions that make it much more difficult to abort a fetus that is incompatible with life during the second trimester. If the pregnant person continues the pregnancy and the results are abnormal, consultations with other providers during the pregnancy will help in developing a plan of care on what actions will be taken at the birth and during the newborn’s hospital stay.

Percutaneous Umbilical Blood Sampling

The percutaneous umbilical blood sampling (PUBS) is a diagnostic test that looks for specific genetic or blood disorders in the fetus. PUBS can be performed starting at 18 weeks’ gestation and is done to diagnose anemia, thrombocytopenia, other blood disorders, chromosomal abnormalities, infection, and isoimmunization in the fetus (Burd, 2016). PUBS provides the most accurate diagnosis of Down syndrome during pregnancy. However, it is not commonly used because it involves more risks than other tests, and it cannot be performed until the second trimester or later in pregnancy (U.S. National Library of Medicine, 2022d). Before the procedure, the health-care provider will discuss the risks versus benefits and obtain informed consent. The nurse will obtain the fetal heart rate and review the pregnant person’s chart for blood type and Rh.

During the procedure, the health-care provider draws a sample of the fetus’s blood directly from the umbilical cord (Figure 13.7). The sample is then sent to the lab to be analyzed for genetic disorders and other fetal health considerations. This procedure can also be used to deliver medications or blood transfusions to a fetus (Burd, 2016).

Image of pregnant person with fetus in utero. Ultrasound wand visible on abdomen. Large needle is being inserted into abdomen, going into the uterus into a blood vessel of the umbilical cord.
Figure 13.7 Percutaneous Umbilical Blood Sampling (PUBS) During a percutaneous umbilical blood sampling, a provider guides a needle, with the aid of an ultrasound, into a blood vessel of the umbilical cord to collect a blood sample. (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

The nurse is often responsible for reinforcing patient education on what to expect before, during, and after the procedure. If the pregnant person is having a PUBS test after 23 weeks’ gestation, they may be instructed not to eat or drink anything several hours before the test in case there are complications during the test that require surgery. During the procedure, the pregnant person will be asked to lie still on an exam table. The provider will clean the pregnant person’s abdomen and apply gel to the abdomen for the ultrasound. A needle will be inserted through the abdomen into a blood vessel in the umbilical cord. The patient may experience brief discomfort during the test. A sample of blood will be collected, the needle will be removed, and the sample will be sent to the lab for testing (U.S. National Library of Medicine, 2022d).

After PUBS, the nurse will monitor the fetal heart rate for a short time. The nurse will also inform the pregnant person that they may experience cramping after the test and should avoid strenuous activity for the rest of the day (U.S. National Library of Medicine, 2022d).

Potential risks of having PUBS include:

  • early delivery via emergent C-section
  • miscarriage
  • blood loss in the fetus and pregnant person
  • cord hematoma
  • slow fetal heart rate
  • infection in the fetus or uterus
  • separation of the placenta from the uterus

The nurse will instruct the pregnant person to watch for any signs or symptoms of infection after the procedure. The pregnant person is advised to call the doctor’s office if they experience chills, cramps that do not get better throughout the day, decreased fetal movement, fever, leaking amniotic fluid, or vaginal bleeding. Results are normally available a few days after the procedure is done. If the results are positive, the provider will go over the results with the pregnant person and may refer the pregnant person and their partner to a genetic counselor for further guidance. Screening and diagnostic tests conducted in the second trimester are summarized in Table 13.4.

Testing Criteria
Screening
Ultrasound
  • Obstetric ultrasound can be performed at any time during the second trimester.
  • It is most often performed at 18–22 weeks’ gestation to assess fetal anatomy for normality.
  • Other reasons for ultrasound are listed previously in this section.
Umbilical Doppler studies
  • This test can be performed starting at 22 weeks’ gestation.
  • It is most often performed when FGR is present to detect the blood flow through the umbilical vessels.
  • Other reasons for Doppler studies are listed previously in this section.
Second trimester marker screening
(integrated screen part 2 or quad screen)
  • This screening is done between 15 and 20 weeks’ gestation.
  • This screening measures the level of alpha-fetoprotein (AFP), estriol (uE3), human chorionic gonadotropin (hCG), and inhibin-A in the pregnant person.
  • These tests screen for Down syndrome, trisomy 18, trisomy 13, other genetic disorders, and neural tube defects.
Second trimester AFP screening
  • This screening is performed at 15-22 weeks’ gestation.
  • Screening is a blood test that screens for fetal neural tube defects.
Diagnostic Tests
Amniocentesis
  • This diagnostic test can be performed after 14–16 weeks’ gestation.
  • It is most often performed to examine fetal cells in a sample of amniotic fluid to detect Down syndrome, trisomy 13, trisomy 18, and other genetic disorders.
Percutaneous umbilical blood sampling (PUBS)
  • This diagnostic test can be performed starting at 18 weeks’ gestation.
  • It is most often performed to diagnose fetal anemia, thrombocytopenia, other blood disorders, chromosomal abnormalities, infection, and isoimmunization.
Table 13.4 Prenatal Screening and Diagnostic Tests in the Second Trimester (ACOG, 2019a)

Antibody Titer

In the second trimester, the pregnant person’s antibody titer, a test for the presence of antibodies to Rh positive blood, is usually done at 26 to 28 weeks’ gestation if they are Rh negative. It is unlikely for health problems to occur if it is the pregnant person’s first pregnancy with an Rh-positive fetus because the pregnant person has not developed enough antibodies to cause harm. However, problems may occur in subsequent pregnancies if treatment is not given. Even if the pregnant person does not carry to full term due to miscarriage, ectopic pregnancy, or induced abortion, problems can occur in subsequent pregnancies without treatment. This problem is known as Rh incompatibility (ACOG, 2022a). At this time the patient’s antibody screen will remain positive for life, and antepartum Rh(D) immune globulin (RhoGAM) will have no effect in preventing isoimmunization in future pregnancies.

If blood from an Rh-positive fetus gets into the bloodstream of an Rh-negative pregnant person, the pregnant person’s body will recognize the fetus’s blood as a foreign substance and will destroy it by making anti-Rh antibodies. These antibodies may cross the placenta into the fetus’s bloodstream and lead to serious health problems in the fetus, or even death of the fetus (ACOG, 2022a).

To prevent isoimmunization problems from occurring due to Rh incompatibility during the third trimester, pregnant persons who are Rh negative should receive antepartum Rho(D) immune globulin (RhoGAM) (ACOG, 2022a). A single dose should be given between 26 and 28 weeks of pregnancy (Yoham & Casadesus, 2023). Antepartum Rh immune globulin should also be given if there are any known or suspected exposures to Rh-positive red blood cells (RBCs) (placental abruption, blunt abdominal trauma, or vaginal bleeding of unknown origin during pregnancy). Rh immune globulin should be given within 72 hours of exposure and then every 12 weeks until delivery. Postpartum administration is necessary only if the infant’s blood is Rh positive.

The nurse is responsible for checking if the patient had their blood type screened to determine if antepartum Rh immune globulin has been administered or is anticipated. The nurse will need to educate the pregnant person on the risks and benefits of receiving the intramuscular (IM) injection, ensure consent to give the injection has been obtained (per facility protocol), and then administer it as ordered by the health-care provider.

Fetoscopy

Inserting a thin fiber-optic tube, or fetoscope, into the uterus through a small incision made in the abdomen of the pregnant person is called fetoscopy (Figure 13.8). Local anesthesia is used during the procedure to minimize discomfort. The fetoscope has a small camera on the end, which allows for visualization of the placenta, amniotic sac, and fetus. This is a diagnostic test that providers may recommend to treat congenital disorders. The fetoscope is hollow, which allows the provider to insert surgical tools through it to repair certain fetal conditions or collect tissue samples. Fetoscopy is performed after 12 weeks’ gestation, depending on the reason it is being done (Ruano & Vega, 2019).

Image of pregnant person with two fetuses in utero. Ultrasound wand visible on abdomen and laparoscope is being inserted into the abdomen, going into the uterus.
Figure 13.8 Fetoscopy During a fetoscopy, a laparoscope is inserted into the uterus to see the fetus and placenta. (attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

A fetoscopy may be recommended for several reasons. Twin-to-twin transfusion syndrome is a condition that can be life-threatening and occurs when identical twins in the womb do not receive an equal share of blood. The use of a fetoscope can help to visualize the placenta and blood vessels that are causing the condition. By using a laser through the fetoscope, the blood vessels that cause uneven blood flow can be closed off (Ruano & Vega, 2019).

In amniotic band syndrome, bands of tissue from the amniotic sac can entangle the fetus, leading to restricted blood flow or even amputation of limbs or organs. A fetoscopy procedure can be used to insert a laser device that cuts and releases the bands of tissue surrounding the fetus (Ruano & Vega, 2019). Fetoscopy may also be done for treatment of placental tumors, spina bifida, and other congenital conditions (Ruano & Vega, 2019).

The nurse has the responsibility to educate the pregnant person on what to expect before, during, and after the procedure in addition to reinforcing the information provided to the pregnant person by the health-care provider on what the risks and benefits of fetoscopy are. Risk factors include rupture of membranes, initiation of labor, or infection. As with other invasive prenatal testing procedures, the nurse also ensures that consent for the fetoscopy has been obtained and provides care to the pregnant person and fetus before, during, and after the procedure.

Magnetic Resonance Imaging

The American College of Obstetricians and Gynecologists (ACOG) recommends performing a magnetic resonance imaging (MRI) exam when an ultrasound scan shows unclear results. Performing MRI for fetal screening may be recommended for the following reasons (Gatta et al, 2022):

  • Central nervous system (CNS) anomalies: If there are any concerns detected by ultrasound or any pathologies that need to be evaluated, an MRI can provide a panoramic view of the entire brain and subarachnoid space without any limitations imposed by the skull. This is especially useful for examining CNS anomalies.
  • Face and neck: If the fetus is in a position where the head and neck are not assessable by ultrasound, MRI can be useful in detecting any abnormalities of the head and neck. MRI can identify issues such as cleft lip and palate, micrognathia or retrognathia, craniosynostosis, cephaloceles, vascular anomalies, tumors, microphthalmia, thyroid anomalies, or oropharyngeal and neck masses.
  • Chest: An ultrasound is the main screening method for thoracic abnormalities like diaphragmatic hernia, cystic adenomatoid malformation, bronchopulmonary seizure, cardiac anomalies or malformations, or cysts or masses that can lead to pulmonary hypoplasia and fetal death. If the ultrasound results come back unclear, an MRI scan may be recommended.
  • Abdomen: Abnormalities in the abdomen can typically be detected after 18 weeks of pregnancy. These may consist of blockages in the esophagus or bowel, masses located within the abdomen, defects in the abdominal wall, bowel obstruction or perforation, peritonitis caused by meconium, as well as renal agenesis or ectopy, duplication of the collecting systems, urinary tract dilatation, ureteroceles, severe cases of vesicoureteral reflux, megaureter, bladder outlet obstruction, or cloacal anomalies.

The nurse is responsible for educating the patient on what to expect during the MRI procedure. There are no risks to the pregnant person or unborn fetus of having an MRI when done in the second and third trimesters (ACOG, 2017b). Once the results of the MRI are available, the health-care provider will review them with the pregnant person if they come back abnormal. The nurse may inform the pregnant person of normal results per facility policy.

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