FETAL ASSESSMENTTo begin this section, we will review the normal development of the fetus. Again, this is only a guide to fetal assessment, and should be used in conjunction with established protocol. Fetal Development:
FETAL CIRCULATION
FETAL HEART TONES This method of testing fetal well-being can be used commencing with the 18th to 20th week of pregnancy. A fetoscope is used for counting the rate. In some cases, ultrasonic equipment may be used to detect fetal heart tones, as early as the 10th week of gestation. However, most nurses will use the standard fetoscope for heart tones. Normal heart tones range between 120 and 160 per minute. Mild bradycardia is considered to be 100 to 119 BPM (beats per minute). Marked bradycardia is considered as 99 or fewer BPM. Marked tachycardia is considered to be 180BPM or higher. This is only a guide; some authorities will use different parameters for diagnosis; be familiar with what is used at your facility to diagnose these conditions. 1. Locate the point of loudest heart tones: Locating this point may be difficult, but with some practice, the nurse can learn to locate that point quickly. Between 10th and 16th weeks, usually an ultrasound device will be used. Between 16th and 24th weeks, search about two fingers above the pubic hairline with the fetoscope. After the 24th week, start at the midline about half way to the umbilicus form the pubic hairline. If nothing is heard at this point, start searching in a rotating circle, becoming increasingly larger in diameter with each swing across the lower abdomen. If you still cannot detect heart tones, you should start a systematic search over the entire abdomen. The fetus can be in such a position that heart tones cannot be heard in the normal area 2. Counting the heart tones: Once located, count the heart tones for a full minute in order to gain the most accurate results. It is acceptable to count for 15 seconds and multiply by 4; or to count for 30 seconds and then multiply by 3 in order to estimate the minute rate. However, it is best to count for a full minute when possible. If there is an irregularity of any kind, always count for a full minute. 3. Considerations:
SERIAL ESTRIOL DETERMINATIONS As the name implies, a series of tests are performed in order to determine estriol levels. Estrogen levels in the urine can fluctuate widely on a daily basis. Therefore, a series of these urine tests are performed in order to obtain an accurate diagnosis. The hormone being sought is Estriol (E3), and is excreted during pregnancy. This hormone requires that the fetus be viable, because it is excreted through the fetus. One single test for E3 is not by itself significant, because as we said, the level will fluctuate. However, very low levels can indicate fetal distress. 24-hour urine specimens are obtained, usually at home, for this test. The test is most helpful in cases of diabetes mellitus; postdate pregnancies, and intrauterine growth retardation cases. It is less helpful for cases of hypertensive diseases, because these need to be diagnosed immediately, and the E3 test determination needs several days minimum from the start of collecting for the test to obtaining the results. ANALYSIS OF AMNIOTIC FLUID Amniocentesis is performed when it is thought that results of the study will outweigh the risks. In early pregnancy, the following may be determined:
In late pregnancy, the following may be determined:
Amniotic fluid studies are not very conclusive by themselves. In combination with other test results, a diagnosis may be made by the physician. The nursing responsibilities will include assisting with the test, preparation of the mother and explanation to the client. Each facility will have its own procedure, become familiar with it and be able to explain all facets to the client. FETAL GROWTH AND MATURITY We have already presented normal characteristics of the fetus and the approximate growth expectations. This section will deal with the nursing factors associated with assessment of the fetus. First we will discuss the EDC and date of delivery. Naegele’s rule for the EDC (expected date of confinement), is:
Most nurses have learned the above formula in their basic nursing programs. You must also remember that the rule is an approximation of the delivery date. In fact, probably less than 5% of all births in this country will occur on the exact date determined by that formula. There are very many factors that influence that date. If the baby is actually born a week or two later or sooner, there is usually no need for concern, since the estimated date is going to be an estimate at best. Factors which can influence the determination of the EDC are numerous, including contraception pills, abnormal periods, abnormal bleeding, disease conditions, and of course, if the woman has poor recollection of when her last period was. It will be helpful if the nurse can obtain the following information:
These and several other factors are important in determining the EDC. The fundal height is one of those factors. When measuring the fundal height, the nurse should remember to place the same amount of pressure on the top of the fundus each time it is measured. The proper way to measure it, is to place one end of a measuring tape on the middle of the upper border of the pubic symphysis and bringing the other end directly over the umbilicus until the upper border of the fundus is reached. The height of the fundus can be expected to become higher as the pregnancy continues. It is also possible however, for the fundus to remain the same height for long periods of time (2-4 weeks). If it should not consistently grow as it was expected, further tests should be done and the physician alerted. If the fundus is consistently lower than expected or higher than expected, there may be an abnormal condition present. THE OXYTOCIN CHALLENGE TEST (OCT) The OCT is also called Stress monitoring. The test delivers an intravenous does of exytocin, which induces uterine contractions. The fetus is monitored during the contractions, and by the way it responds, the physician can predict the well-being of the fetus. The protocol for the nurse is different at each facility; usually the client is given a very light meal the night before the test. However, some places prefer that she remain NPO. A signed permit usually is required, since there is a slight risk with the procedure. The nurse will monitor the mother as the physician monitors the recording device for the fetal heat tones and rate. The test results of negative means that no significant changes were noted in the fetal heart rate when the contractions were induced, and the fetus is probably well and safe for labor. If the test results are positive, it indicates that there are significant changes in the heart rate of the fetus, and the fetus may be in danger. If other tests also confirm fetal distress, the physician will usually decide to terminate the pregnancy then, and deliver the infant. Stress monitoring tests are carried out routinely in many places today. They are relatively safe, however, the nurse must remember to constantly monitor the patient. There are many adverse conditions which can occur. In fact, labor may be induced by the administration of the drug, since this test is usually performed late in pregnancy. So always be ready for any emergency in conjunction with this test. SPECIAL CHARACTERISTICS AND GOALS OF ASSESSMENT OF THE FETUS At the present time, there is tremendous disagreement among physicians about testing for fetal well-being. Various combinations of tests seem to be the only agreement among physicians, meaning that no one test should be relied upon. Rather a series of tests, or combination of tests should be given if fetal distress is suspected. If you as a nurse are unsure as to the implications of these tests or as to their results, review their implications in any basic obstetrical nursing textbook. When tests indicate that the fetus is not doing well, the physician must determine the risks involved with the termination of pregnancy. The physician will weight all of the factors such as the relative hostility of the uterine environment, the other risk factors, before deciding to terminate the pregnancy. Please review basic anatomy and physiology of labor and delivery if you are unsure of the particular risks involved with terminating the pregnancy early. These are the pertinent facts:
Most hospitals today use the scalp clip connected to the fetal monitoring system; review the methods and nursing implications if you are interested in that area of nursing. It is too lengthy a subject for us to detail in this course. Next: NEWBORN ASSESSMENT |
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