Ultrasound, Biophysical Profile, Obstetric(redirected from OB sonography)
Ultrasound, Biophysical Profile, Obstetric
Area of applicationPelvis and abdominal region.
Obstetric US is used to secure different types of information regarding the fetus and placenta, varying with the trimester during which the procedure is done. This procedure may also include a nonstress test (NST) in combination with Doppler monitoring of amniotic fluid volume, fetal heart, gross fetal movements, fetal muscle tone, and fetal respiratory movements to detect high-risk pregnancy. The procedure is indicated as a guide for amniocentesis, cordocentesis, fetoscopy, aspiration of multiple oocytes for in vitro fertilization, and other intrauterine interventional procedures.
The biophysical profile (BPP) considers five antepartum parameters measured to predict fetal wellness. The BPP is indicated in women with high-risk pregnancies to identify a fetus in distress or in jeopardy of demise. It includes fetal heart rate (FHR) measurement, fetal breathing movements, fetal body movements, fetal muscle tone, and amniotic fluid volume. Each of the five parameters is assigned a score of either 0 or 2, allowing a maximum or perfect score of 10. The NST is an external US monitoring of FHR performed either as part of the BPP or when one or more of the US procedures have abnormal results. The NST is interpreted as either reactive or nonreactive.
|BPP Parameter||Normal: Score = 2||Abnormal: Score = 0|
|Fetal heart rate reactivity||Two or more movement-associated FHR accelerations of 15 or more beats/min above baseline, lasting 15 sec, in a 20-min interval||One or no movement-associated FHR accelerations of 15 or more beats/min above baseline in a 20-min interval|
|Fetal breathing movements||One or more breathing movements lasting 20–60 sec in a 30-min interval||Absent or no breathing movements lasting longer than 19 sec in a 30-min interval|
|Fetal body movements||Two or more discrete body or limb movements in a 30-min interval||Less than two discrete body or limb movements in a 30-min interval|
|Fetal muscle tone||One or more episodes of active limb extension and return to flexion (to include opening and closing of hand)||Absent movement, slow extension with partial return to flexion, partial opening of hand|
|Amniotic fluid volume||One or more pockets of fluid that are 2 cm or more in the vertical axis||No pockets of fluid or no pocket measuring at least 2 cm in the vertical axis|
A contraction stress test (CST or oxytocin challenge test) may be requested in the event of an abnormal fetal heart rate in the BPP or NST. The CST is used to assess the fetus’s ability to tolerate low oxygen levels as experienced during labor contractions. The CST includes external FHR monitoring by US and measurement of oxytocin (Pitocin)-induced uterine contractions. Pressure changes during contractions are monitored on an external tocodynamometer. Results of the two tests are interpreted as negative or positive. A negative or normal finding is no late decelerations of FHR during three induced contractions over a 10-min period. A positive or abnormal finding is identified when frequent contractions of 90 sec or more occur and FHR decelerates beyond the time of the contractions. The amniotic fluid index (AFI) is another application of US used to estimate amniotic fluid volume. The abdomen is divided into four quadrants using the umbilicus to delineate upper and lower halves and linea nigra to delineate the left and right halves. The numbered score is determined by adding the sum in centimeters of fluid in pockets seen in each of the four quadrants. The score is interpreted in relation to gestational age. The median index is considered normal between 8 and 12 cm. Oligohydramnios (too little amniotic fluid) is associated with an index between 5 and 6 cm, and polyhydramnios (too much amniotic fluid) with an index between 18 and 22 cm.
This procedure is contraindicated for
- Detect blighted ovum (missed abortion), as evidenced by empty gestational sac
- Detect fetal death, as evidenced by absence of movement and fetal heart tones
- Detect fetal position before birth, such as breech or transverse presentations
- Detect tubal and other forms of ectopic pregnancy
- Determine and confirm pregnancy or multiple gestation by determining the number of gestational sacs in the first trimester
- Determine cause of bleeding, such as placenta previa or abruptio placentae
- Determine fetal effects of Rh incompatibility due to maternal sensitization
- Determine fetal gestational age by uterine size and measurements of crown-rump length, biparietal diameter, fetal extremities, head, and other parts of the anatomy at key phases of fetal development
- Determine fetal heart and body movements and detect high-risk pregnancy by monitoring fetal heart and respiratory movements in combination with Doppler US or real-time grayscale scanning
- Determine fetal structural anomalies, usually at the 20th week of gestation or later
- Determine the placental size, location, and site of implantation
- Differentiate a tumor (hydatidiform mole) from a normal pregnancy
- Guide the needle during amniocentesis and fetal transfusion
- Measure fetal gestational age and evaluate umbilical artery, uterine artery, and fetal aorta by Doppler examination to determine fetal intrauterine growth retardation
- Monitor placental growth and amniotic fluid volume
- Normal age, size, viability, position, and functional capacities of the fetus
- Normal placenta size, position, and structure; adequate volume of amniotic fluid
- BPP score of 8 to 10 is considered normal. Each of the fetal movements evaluated in the BPP is related to oxygen-dependent activities that originate from the central nervous system. Their presence is assumed to indicate normal brain function and absence of systemic hypoxia.
Abnormal findings related to
- Abruptio placentae
- Cardiac abnormalities
- Ectopic pregnancy
- Fetal death
- Fetal deformities (organs or skeleton)
- Fetal hydrops (non-immune)
- Fetal intestinal atresia
- Fetal malpresentation (breech, transverse)
- Multiple pregnancy
- Placenta previa
- Renal or skeletal defects
- BPP score between 4 and 6 is considered equivocal. Gestational age is important in determining intervals for retesting and/or a decision to deliver.
- Abruptio placentae
- BPP score between 0 and 2 is abnormal and indicates the need for assessment and immediate delivery.
- Ectopic pregnancy
- Fetal death
- Placenta previa
It is essential that a critical finding be communicated immediately to the requesting health-care provider (HCP). A listing of these findings varies among facilities.
Timely notification of a critical finding for lab or diagnostic studies is a role expectation of the professional nurse. Notification processes will vary among facilities. Upon receipt of the critical value the information should be read back to the caller to verify accuracy. Most policies require immediate notification of the primary HCP, Hospitalist, or on-call HCP. Reported information includes the patient’s name, unique identifiers, critical value, name of the person giving the report, and name of the person receiving the report. Documentation of notification should be made in the medical record with the name of the HCP notified, time and date of notification, and any orders received. Any delay in a timely report of a critical finding may require completion of a notification form with review by Risk Management.
- Patients with latex allergy; use of the vaginal probe requires the probe to be covered with a condom-like sac, usually made from latex. Latex-free covers are available.
Factors that may impair clear imaging
- Incorrect placement of the transducer over the desired test site; quality of the US study is very dependent upon the skill of the ultrasonographer
- Metallic objects (e.g., jewelry, body rings) within the examination field, which may inhibit organ visualization and cause unclear images
- Inability of the patient to cooperate or remain still during the procedure because of age, significant pain, or mental status
- Retained gas or barium from a previous radiological procedure
- Dehydration, which can cause failure to demonstrate the boundaries between organs and tissue structures
- Insufficiently full bladder, which fails to push the bowel from the pelvis and the uterus from the symphysis pubis, thereby prohibiting clear imaging of the pelvic organs in transabdominal imaging
>Factors that may result in incorrect values
- Absence of activity in a particular parameter of the BPP may be related to fetal sleep pattern; gestational age less than 33 wk or greater than 42 wk; maternal ingestion of glucose, nicotine, or alcohol; maternal administration of magnesium or medications; artificial or premature rupture of membranes; and/or labor.
- Patients who are very obese, who may exceed the weight limit for the equipment.
Nursing Implications and Procedure
- Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
- Patient Teaching: Inform the patient this procedure can assess abdomen and pelvic organ function.
- Obtain a history of the patient’s complaints or clinical symptoms, including a list of known allergens, especially allergies or sensitivities to latex.
- Obtain a history of the patient’s reproductive system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
- Note any recent procedures that can interfere with test results (i.e., barium procedures, surgery, or biopsy). There should be 24 hr between administration of barium and this test.
- Endoscopic retrograde cholangiopancreatography and colonoscopy, if ordered, should be scheduled after this procedure.
- Record the date of the last menstrual period. Obtain a history of menstrual dates, previous pregnancy, and treatment received for high-risk pregnancy.
- Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
- Review the procedure with the patient. Address concerns about pain related to the procedure and explain that some pain may be experienced during the test, and there may be moments of discomfort. Inform the patient the procedure is performed in a US department, usually by an HCP specializing in this procedure, and takes approximately 30 to 60 min.
- For the transvaginal approach, inform the patient that a sterile latex- or sheath-covered probe will be inserted into the vagina.
- Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
- Instruct the patient receiving transabdominal US to drink three to four glasses of fluid 90 min before the procedure, and not to void, because the procedure requires a full bladder. Patients receiving transvaginal US only do not need to have a full bladder.
- Instruct the patient to remove jewelry and other metallic objects from the area to be examined prior to the procedure.
- Note that there are no food or medication restrictions unless by medical direction. The test may be scheduled in relation to mealtime because fetal activity is highest 1 to 3 hr after the mother ingests a meal.
- Potential complications: N/A
- Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient.
- Ensure that the patient has removed all external metallic objects from the area to be examined prior to the procedure.
- Ensure that the patient receiving transabdominal US drank three to four glasses of fluid and has not voided.
- Instruct the patient to change into the gown, robe, and foot coverings provided.
- Instruct the patient to cooperate fully and to follow directions. Ask the patient to remain still throughout the procedure because movement produces unreliable results.
- Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
- Place the patient in the supine position on an examination table. The right- or left-side-up position may be used to allow gravity to reposition the liver, gas, and fluid to facilitate better organ visualization.
- Expose the abdominal area and drape the patient.
- Transabdominal approach: Conductive gel is applied to the skin, and a transducer is moved over the skin while the bladder is distended to obtain images of the area of interest.
- Transvaginal approach: A lubricated, covered probe is inserted into the vagina and moved to different levels to obtain images.
- Ask the patient to breathe normally during the examination. If necessary for better organ visualization, ask the patient to inhale deeply and hold her breath.
- Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
- Allow the patient to void, as needed.
- When the study is completed, remove the gel from the skin.
- Recognize anxiety related to test results. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Encourage the family to seek appropriate counseling if concerned with pregnancy termination and to seek genetic counseling if a chromosomal abnormality is determined. Decisions regarding elective abortion should take place in the presence of both parents. Provide a nonjudgmental, nonthreatening atmosphere for discussing the risks and difficulties of delivering and raising a developmentally challenged infant and for exploring other options (termination of pregnancy or adoption). It is also important to discuss problems the mother and father may experience (guilt, depression, anger) if fetal abnormalities are detected.
- Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
- Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. There are numerous tests for fetal genetic testing associated with inherited diseases and congenital abnormalities. The tests can be performed from amniotic fluid by methods that include polymerase chain reaction, microarray, and cell culture with karyotyping comparison. Evaluate test results in relation to the patient’s symptoms and other tests performed.
- Related tests include amniotic fluid analysis and L/S ratio, biopsy chorionic villus, blood groups and antibodies, chromosome analysis, culture bacterial anal/genital, culture viral, fetal fibronectin, α1-fetoprotein, hexosaminidase A and B, human chorionic gonadotropin, KUB, Kleihauer-Betke test, MRI abdomen, and prolactin.
- Refer to the Reproductive System table at the end of the book for related tests by body system.