Identification And Antepartum Surveillance of the High-Risk Patient

Identification Of The High Risk Patient

Several high-risk identification systems have been proposed by different authors. (Aubry, 1973, Hobel,1973 and Good win, 1969) Most of these systems give different numerical values to the high-risk factors.

Some of the commercially available prenatal records have incorporated high-risk scoring systems to allow the classification of patients into high- and low-risk categories.

A useful system is a modification of the high-risk scoring system proposed by Coopland et al. (1977) in Mantitoba, Canada. This scoring system takes into consideration several different factors, which are each given a numerical value from one to five, depending on their potential impact on the outcome of the pregnancy. A score of seven or more indicates, in the majority of cases, the need for referral to a maternal-fetal medicine specialist.

High Risk Evaluation Form

Name		Age		Gravida		Para
Aborta		LMP		EDC		EDC by ultrasound
Reproductive history			Medical or surgical associated conditions				Present pregnancy
Age:	< 16 = 1 16-35=0 > 35 =2__		Previous gynecologic surgery		=1_		Bleeding <20 weeks >20 weeks	=1__ =3__
Parity:	0 = 1 1-4= 0 > 5= 2__		Chronic renal disease		=1_		Anemia (<10g %)	=1__
Two or more abortions or history of infertility	= 1 __		Gestational diabetes (A)		=1_		Postmaturity Hypertension	=1__ =2__
Postpartum bleeding or manual removal	= 1 __		Class B or greater diabetes		=3_		Premature rupture of membranes	=2__
Child >9 lb	= 1__		Cardiac disease		=3_		Polyhydram-nios	=2__
Child <5 lb	= 1__		Other significant medical disorders		=__		IUGR	=3__
Toxemia or hypertension	= 2__		(Score 1 to 3 according to the severity)				Multiple pregnancy	=3__
Previous cesarean section	= 2__						Breech or malpresent-ation	=3__
Abnormal or difficult labor	= 2__						Rh isoimm-unization	=3__
Column Totals	_____		______					____
Total Score (sum of the three columns)	________						Low risk High risk Severe risk	0-2 3-6 7 or more

The following patients should be referred to a specialist in maternal-fetal medicine:

1.Those, with conditions that may require invasive procedures for fetal diagnosis or therapy, such as:

¨1Rh isoimmunization

¨2Fetal urinary tract obstruction

¨3Fetal congenital heart block

¨4Fetal hydrocephaly

1.Those with severe medical complications affecting the mother, such as:

¨1Brittle diabetes

¨2Cardiac disease grades III and IV

¨3Artificial heart valves

¨4Sickle cell disease

1.Those with recurrent poor obstetrical outcomes, such as:

¨1Habitual abortion

¨2Failed cerclages

¨3Recurrent stillborns

¨4Recurrent early rupture of membranes

¨5Recurrent preterm labor

1.Those with obstetrical complications that require specialized care for adequate management, such as:

¨1Severe preeclampsia or eclampsia with renal failure,

¨2pulmonary edema,

¨3hypertension unresponsive to treatment,

¨4Severe fetal growth retardation

¨5Multiple high-risk factors

Once a high-risk patient is identified, the physician and the nurse must explain to the patient and her husband the potential effects of her high-risk factors(s) on the outcome

of pregnancy and the effects that pregnancy may have on the maternal condition. In all cases the information provided to the patient should be given in simple terms.

Preconception counseling

Ideally, the patient with multiple or severe high-risk factors should be counseled before pregnancy occur. Taysi K (1988). When preconception counseling is possible, the nurse should have a relaxed interview with the patient and her husband to discuss the following points:

1. The importance of high-risk factors identified in the history and physical examination of the patient

2. The potential effects that each risk factor may have on the pregnancy

3. The effect that the pregnancy may have on each of the identified risk factors

4. Potential maternal disability during pregnancy and the length of that disability

5. The special test that will be required for monitoring maternal and fetal well-being during pregnancy

6. The prognosis for a successful fetal and maternal outcome

7. The cost of the pregnancy including additional testing and consultation required as well as the cost of neonatal intensive care if preterm delivery is a significant possibility

Methods Of Fetal Surveillance For High-Risk Patients

The objectives of antepartum surveillance in the high-risk patient are:

1. To determine gestational age.

2. To discover fetal congenital abnormalities.

3. to detect abnormalities in fetal growth.

4. To detect and determine the severity of acute and chronic fetal asphyxia.

Determination of gestational age

An accurate establishment of the expected date of delivery (EDD) is fundamental to the management of high-risk pregnancies. Proper assignment of EDD is necessary to obtain and appropriately interpret laboratory tests, to plan and execute therapeutic maneuvers, and to determine the optimal management in certain difficult situations.

The methods used to achieve the fourth objectives in the antepartum care of the high-risk patient-that is, to detect and evaluate the severity of acute or chronic fetal hypoxia-are all biophysical in nature. They have completely re[placed biochemical tests (estriol, human placental lactogen), which are obsolete and known to be unreliable. The tests used at the present time are:

1. Nonstress test (NST)

2. Contraction stress test (CST)

3. Fetal biophysical profile (BPP)

4. Vibroacoustic stimulation test (VAST)

5. Modified biophysical profile (MBPP)

6. Umbilical and uterine Doppler ultrasound

7. Fetal movement count (FM)

8. Percutaneous umbilical blood sampling (PUBS)

The non stress test is the test most commonly used for antepartum evaluation of fetal well-being. The rationale underlying this test is that the presence of spontaneous fetal rate accelerations associated with fetal movements (fetal reactivity) is an indicator of fetal well-being. Likewise, the absence of fetal reactivity suggests the possibility of fetal distress and warrants further investigation

How to Do an NST

1. Place patient in the semi-Fowler’s position. Use pillows under one of her hips to displace the weight of the uterus away from the inferior vena cava. Take the patient’s blood pressure every 10 minutes during the procedure

2. Apply the tocoacardiographic equipment to the maternal abdomen, and observe the uterine activity and FHR for 10 minutes. Instruct the patient to push the calibration button of the uterine contraction tracing every time she feels FM.

3. A reactive test is present two or when two or more FHR accelerations are clearly recorded during a 20-minute period, each acceleration of 15 or more beats per minute and lasting 15 or more seconds, usually occurring simultaneously with episodes of fetal activity.

4. If no spontaneous FM occurs during the initial 20 minutes of observation, the test is continued for another 20 minutes, and during this period FM is provoked by external manipulation. If there is no acceleration with spontaneous or repeated external stimuli during a 40-minute period, the test is considered nonreactive.

5. The test is unsatisfactory if the quality of the monitor trace is inadequate for interpretation.

The NST is noninvasive, easily performed and interpreted, and readily accepted by patients. The false-negative rate of the test (reactive NST in a fetus who actually in distress) is 3.2 per 1000, indicating that the likelihood of fetal death or serious fetal morbidity following a negative reactive test is extremely low. The false-positive rate (nonreactive results in normal patients) is very high: 50% for morbidity and 80% for mortality, indicating that the probability of serious fetal problems when the test is positive (nonreactive) is low.

¨The variables that must be evaluated are:

1.Baseline fetal heart rate

2.Variability of the fetal heart rate

3.Presence or absence of accelerations

4.Presence or absence of decelerations

A normal baseline heart rate is between 120 and 160 beats per minute (bpm). The abnormal alterations are tachycardia (frequency greater than 160 bpm) and bradycardia (frequency less than 120 bpm).

Modern fetal heart monitoring equipment allows, under most circumstances, adequate evaluation of variability using indirect recording of the FHR obtained with Doppler ultrasound. FHR variability de[ends on the interaction of the fetal sympathetic and parasympathetic system and is influenced by gestational age, maternal medications, fetal congenital anomalies, fetal acidosis, and fetal tachycardia.

The presence of accelerations in the FHR associated with fetal movements or in response to fetal stimulation is a reliable sign of fetal health

A problem with the definition of accelerations in the NST has been clarified. The study of Wills et al. (1990) demonstrated that the “short criterion” (15 seconds from beginning of acceleration to return to baseline) and the “long criterion” (acceleration maintained at 1 bpm above the baseline for 15 seconds) for the duration of FHR accelerations have the same sensitivity, specificity, and positive and negative

The Contraction stress test (CST) is one of the best available tests for the primary fetal surveillance of high-risk pregnancies. The test is based on experimental evidence showing that the uteroplacental blood flow decreases markedly or ceases during uterine contractions cause a hypoxic stress that a normal, healthy fetus can tolerate without difficulty. In contrast, a fetus with chronic or acute problems will not be able to tolerate such a decrease in oxygen supply and will demonstrate this by decelerations of the FHR following the contractions

The false-negative rate of the CST is 0.4 per 1000, significantly better than that of the NST. However, the false-positive rate with respect to fetal morbidity is 50% , similar to that of the NST.

The end point of the CST is the presence or absence of late decelerations of the FHR following uterine contractions induced by intravenous oxytocin (OCT) or by nipple stimulation.

How to Do a CST or an OCT

1. Place patient in semi-Fowler’s position. Use pillows under the patient’s hip or side to displace the weight of the uterus away from the inferior vena cava. Take the patient’s blood pressure every 10 minutes throughout the test.

2. Apply the tococardiographic equipment, to the maternal abdomen, and observe the uterine activity and the FHR for approximately 15 to 20 minutes. Many patients who are receiving the test because of nonreactive NST show adequate fetal reactivity during this observation period and do not require oxytocin stimulation. Other patients show spontaneous uterine activity of sufficient frequency and duration and do not require oxytocin administration.

3. Start intravenous oxytocin administration using a Harvard pump at 0.5 mU/minute. Double the rate every 15 to 20 minutes until three contractions lasting 40 to 60 seconds occur within a 10-minute period. If late decelerations appear before this duration and frequency of contractions have been achieved, the administration of oxytocin must be interrupted. Massage of the nipples with a warm towel by the patient may be all that is necessary to provoke uterine contractions and avoid the use of oxytocin.

The biophysical profile (BPP) is an excellent test for the evaluation of fetal well-being. It entails the observation by ultrasound of fetal breathing movements, fetal body movements, fetal tone, amniotic fluid volume, and FHR reactivity.

These factors are dependent on the integrity of the fetal central nervous system and are affected in situations of fetal compromise.

The test is easy to perform, requires no immediate supervision by a physician, can be quickly done in the physician’s office, has no contraindications, and involves no risk for the mother or the fetus.

The false-negative rate of the BPP is 0.7 per 1000, a value significantly better than that of the NST and similar to that of the CST. The false-positive rate of the BPP is approximately 30 %, significantly better than that of the NST or the CST.

Fetal Biophysical Profile

1. Fetal breathing movement---30 seconds of sustained breathing movement during a 30-minute observation period

2. Fetal movement--- Three or more gross body movements in a 30-minute observation period

3. Fetal tone--- One or more episodes of limb motion from a position of flexion to extension and a rapid return to flexion

4. Fetal reactivity--- Two or more FHR accelerations associated with fetal movement of at least 15 bpm and lasting at least 15 seconds in 10 minutes (reactive NST)

5. Fluid volume--- Presence of a pocket of amniotic fluid that measures at least 1 cm in two perpendicular planes

The main problem with the is the structure of the test, in which each of the five criteria (fetal breathing movements, fetal body movements fetal tone, amniotic fluid volume, and FHR reactivity) is assigned a score of either zero or two points, despite the possibility that each of those variables may have different importance in assessing the fetal situation.

¨The BPP variables are dependent on the activity of certain areas of the fetal central nervous system that become functional at different gestational ages.

¨Fetal tone and movement appear between 7 and 9 weeks and require activity of the brain cortex. Fetal breathing movements begin at 20 to 21 weeks and depend on centers in the ventral surface of the fourth ventricle.

¨FHR reactivity appears between 28 and 30 weeks and probably stems from

¨function of the posterior hypothalamus and nucleus in the upper medulla.

Vibroacoustic stimulation was originally designed to decrease the time spent in the performance of NST_S because of prolonged episodes of fetal sleep periods during the test. The results obtained with vibroacoustic stimulation have been excellent. The NST with the vibroacoustic stimulation test (VAST) is substituting the classical NST as the test most commonly used for antepartum fetal surveillance. The test uses stimulation with an artificial larynx over the fetal head for 1 to 3 seconds. This instrument produces a vibratory acoustic stimulus of approximately 80 H_Z and 82dB. A healthy fetus will respond with sudden movement (startle response) followed by acceleration of the fetal heart rate.

According to Crade and Lovett, (1988) fetuses of less than 24 weeks do not respond to vibroacoustic stimulation. Between 24 and 27 weeks of gestation, 30 % of all fetuses will respond to the vibroacoustic stimulation. Between 27 and 30 weeks, 86 % will respond to the artificial larynx. In the majority of cases, the acceleration of the fetal heart rate that follows vibroacoustic stimulation lasts for several minutes. Another normal fetal response is a series of two to five accelerations lasting 20 to 60 seconds each. Maternal perception of fetal movement following vibroacoustic stimulation is another indicator of fetal well-being.

There are several factors that may influence the result of VAST. Examples of these are the thickness of the maternal abdominal wall, the amount of amniotic fluid, the pressure exerted by the examiner in holding the artificial larynx against the abdomen, and the intensity of the stimulation. The influence of these factors is small, since only 2% of NST_S are nonreactive following VAST.

Vintzileos et al. (1987) were the first to propose a modification of the biophysical profile for evaluation of fetal well-being.

The modified biophysical profile (MBPP) is the best available test for primary fetal surveillance. It combines the observation of an index of acute fetal hypoxia, the NST with VAST, and a second index indicative of chronic fetal problems, the amniotic fluid volume.

The test has excellent negative and positive predictive values, is easy to interpret, has clearly defined end points, and can be performed in an average of 20 minutes.

How to Do a Modified Biophysical Profile

Start NST in the standard manner. If a spontaneous acceleration is not seen within 5 minutes, a single 1- to 2-second sound stimulation is applied in the lower abdomen with the artificial larynx. This stimulus may be repeated up to three times if necessary.

Since this procedure requires two accelerations within 10 minutes for a definition of reactivity, a second stimulus is applied if 9 minutes have elapsed since the first acceleration. Accelerations are defined in the standard manner of 15 bpm amplitude from an established baseline lasting 15 seconds,

Then a four-quadrant amniotic fluid volume is assessed by placing a linear ultrasound transducer perpendicular to the wall of the uterus and parallel to the mother’s spine in four abdominal quadrants and measuring the largest vertical amniotic fluid pocket.

Pockets consisting primarily of umbilical cord are disregarded. A four-quadrant sum of 5 cm or greater is considered normal.

The following guidelines are used in regard to using the MBPP as the primary test for fetal surveillance:

1.If both tests are normal, weekly fetal surveillance with MBPP is continued.

2.If both tests are abnormal (nonreactive NST, decreased amniotic fluid volume) and the pregnancy is 36 weeks or more, the patient should be delivered. If the pregnancy is less than 36 weeks, the management is individualized. Amniocentesis, daily testing, performance of CST, or delivery may be used depending on the circumstances.

3.If the amniotic fluid volume is decreased but the NST is reactive, a search for chronic fetal conditions, particularly congenital abnormalities, is undertaken; and the frequency of testing with MBPP is increased to twice weekly.

4.If the amniotic fluid volume is normal and NST is nonreactive, further testing with CST or full BPP is indicated.

The introduction of Percutaneous umbilical blood sampling (PUBS) by F. Daffos in 2983, and the confirmation by the same investigator in 1985 of the safety of the procedure, has opened new avenues to the field of fetal diagnosis. The availability of this technique has changed the management of patients with RH isoimmunization, idiopathic thrombocytopenic purpura (ITP), toxoplasmosis, and hereditary blood disorders.

PUBS can be performed easily after 24 weeks of gestation. Attempts are being made in many centers to perform the procedure as early as 16 weeks, but in most cases it can consistently be done only after 18 weeks. PUBS can be performed at any point in the cord, but the placental insertion site is preferred. The procedure requires the use of high-resolution ultrasound equipment. Most investigators use sector scanning, free-hand technique, and a 22-gauge needle.

The safety of PUBS has not been completely established. Preliminary reports on a few thousand samplings have indicated that the procedure has a risk of one fetal

death per 300 PUBS, the same as ultrasound-guided genetic amniocentesis. Some recent information, however, suggests that the mortality may be as high as 5 %.

The indications for the use of PUBS will expand with further experience with the procedure.

Indications for Percutaneous

Umbilical Blood Sampling (PUBS)

1.Rapid karyotype in fetuses with structural abnormalities discovered during ultrasound examination

2.Fetal hemolytic disease

3.Suspected fetal viral infection

4.Nonimmunologic hydrops fetalis

5.Suspected fetal thrombocytopenia

6.Diagnosis of twin-to-twin transfusion

7.suspected fetal hemoglobinopathy