Tests Of Fetal Well-being Research Articles

1 Biochemical methods

Biochemical tests of fetal well-being are falling into disfavour. Difficulties arise because we are unable to ascribe specific functions to most test substances, and because they have a large normal range. Nevertheless, a critical survey of the evidence suggests biochemical tests have a part to play in antenatal monitoring, albeit a much reduced one. The main test substances are steroids and proteins produced by the trophoblast. These two classes of substances have a quite different metabolism and compartmental distribution, and the appropriate application of assays is different. A variety of progestogens and oestrogens are used as test substances, the most notable being oestriol. In view of their rapid metabolism, steroid assays serve best in pathological conditions of rapid onset. A dynamic test of the conversion of dehydroepiandrosterone to oestradiol has not fulfilled its initial promise. Among the placental proteins, human placental lactogen is most favoured, although some of the newly discovered proteins may have special applications in certain diseases. The use of biochemical tests in early pregnancy has not been sufficiently explored. The test substances may, in early pregnancy, play a more important role in fetal development and biochemical tests, particularly as a screening test to detect patients at risk of later overt disease, may be valuable.

Intrapartum vibroacoustic stimulation in cases of normal and abnormal fetal heart rate patterns.

The fetal heart rate (FHR) response to a vibroacoustic stimulation was studied in 100 women during active labor. Three types of FHR responses were noted: acceleration, tachycardia of duration longer than 2 min, and combined acceleration-deceleration response. The last type was significantly more common in labors with abnormal FHR tracings. All fetuses demonstrating FHR response to the stimulation, including those with abnormal FHR tracings, had good outcome. The vibroacoustic stimulation is easily performed, noninvasive, and has no contraindications. Its possible application as an intrapartum test of fetal well-being awaits further clinical confirmation.

Indications for and timing of delivery in diabetic pregnancies

The management of 430 diabetic pregnancies is presented. Our protocol emphasized “tight” metabolic control and assessment of fetal well-being by antepartum fetal heart rate testings and estriol levels. Spontaneous labor was allowed in uncomplicated Class A diabetic patients. Labor in complicated cases and insulin-dependent diabetic pregnancies was induced after establishing fetal lung maturity, except when a maternal or fetal complication dictated otherwise. A significant drop in estriol was observed in 4% of Class A diabetic patients and 10.2% of insulin-dependent diabetic patients. None developed a positive contraction stress test. Abnormal fetal well-being tests contributed minimally to the indications for induction of labor. The incidence of induced preterm delivery was 2.8% in Class A diabetic patients and 18.4% in insulin-dependent diabetic ones. The perinatal mortality was 5.6 : 1000 and 13 : 1000, respectively. The incidence of respiratory distress syndrome was very low, and none of the cases were associated with a “mature” amniotic fluid lecithin phosphorus measurement.

Prenatal Assessment of Gestational Age:

Despite extensive technological advances in the assessment of fetal well-being and maturity, iatrogenic prematurity and associated respiratory distress syndrome (RDS) remains the primary causes of perinatal mortality and morbidity. Much variation exists regarding selection criteria, administration, precision, and interpretation of individual and combined gestational age determinants. Although obstetrical physical examination and menstrual history remain the mo9st consistently used fetal dating methods, reliability and validity of these procedures have not been systematically examined on a large scale. Laboratory studies (ultrasound measures, amniotic fluid determinants, maternal serum and urine component values) have been more appropriately standardized for specific populations, although lack of agreement persists among authors with regard to test methods and interpretation of test results. The distinction between tests of fetal well-being versus fetal maturity emphasizes the importance of reviewing the p...

10 - Ultrasonic Assessment of Fetal Activity

Modern ultrasound techniques enable dynamic studies of fetal activity in utero to be studied and quantified. Real-time B-mode scanning has become the method of choice for this purpose because of its ease of use and precision. Fetal movements can be visualized as early as in the seventh week of pregnancy and the development of the movement patterns can be followed throughout the pregnancy. Up to 16 types of movements have been described by several research groups. In early pregnancy, the finding of normal fetal movements is a good prognostic sign in cases of threatened abortion. A decrease in the movement incidence or a qualitative change of the movements are associated with poor outcome. In late pregnancy, the mean incidence of general fetal movements has been found on average to be 9 to 18 per cent of observation time. Fetal breathing movements, mainly with typical "see-saw' configurative changes of the fetal trunk, occur episodically: both long-term and short-term periodicity have been revealed. For recognition of the time incidence pattern of fetal movements or breathing, a sufficiently long observation time (80 to 100 minutes) is necessary. The incidence of fetal breathing movements increases with gestational age and breathing movements become more regular in mature fetuses. Fetal motor activity is subject to several external influences: glucose given to the mother causes an increase in the fetal breathing movement incidence; maternal hypercarbia stimulates the fetal breathing movements; alcohol administered to the mother abolishes fetal breathing; maternal smoking changes the time spacing of breathing and increases the fetal breathing rate; and exposure of the fetus to sound causes an increase in the number of movements. Real-time ultrasonography enables detection and recording of several other fetal activities: hiccups, swallowing and changes in the stomach volume, micturition, and fetal eye movements. The latter fetal activity is used together with fetal movements, fetal mouth movements and fetal heart rate for the identification of the fetal behavioural states. Quantification of fetal activity as a clinical test of fetal well-being was expected to give an alarm signal in cases of fetal hypoxia and imminent asphyxia. In general, the predictive value of a negative result (i.e., a finding of normal fetal activity) was high; the predictive value of decreased or abnormal fetal activity was found to be much less predictive of fetal compromise.(ABSTRACT TRUNCATED AT 400 WORDS)

The nonstress test: The false negative test

The nonstress test (NST) has been shown to be a reliable technique for the evaluation of fetal status. As a rule, a reactive NST, as opposed to a nonreactive NST, has been associated with a good pregnancy outcome. Nonetheless, fetal death has followed a reactive test. Because of the uncommon occurrence of a false negative NST, a retrospective investigation of the 2,226 patients who had undergone 4,500 NSTs was undertaken. Of these high-risk pregnancies, 1,564 women were delivered within 7 days of a reactive NST and there were four fetal deaths (0.026%). The presumed etiology for the four deaths was cord accident in three cases and abruptio placentae in one case. As with the false negative contraction stress test, the false negative NST appears to be associated with cord accidents, congenital anomalies, and abruptio placentae. Even though a reactive NST is associated with a low incidence of fetal death, close attention to the presence of fetal heart rate decelerations on the NST may be helpful in identifying those patients at risk for a cord accident and, theoretically, in reducing the incidence of fetal death. Even then, certain unavoidable situations can occur soon after a reactive NST, and, at present, no test of fetal well-being offers complete reassurance.

Antenatal detection of growth retardation: actual practice in a large maternity hospital.

A retrospective analysis of the antenatal management of 226 cases of growth retardation was carried out. One-hundred-and-fourteen cases (50%) were not suspected antenatally. Of the 112 suspected cases, 107 were subjected to further tests of fetal well-being. Eighty-one (72%) of the 112 received no further action or surveillance because of erroneously reassuring results or no further tests. Thirty-one women were either admitted antenatally (15) or delivered early (16). The low rate of initial suspicion combined with the disappointing results of the further tests emphasizes the need for more accurate screening procedures for growth-retarded babies.

Sensitivity, Specificity, and Predictive Accuracy as Measures of Efficacy of Diagnostic Tests

ABSTRACT The proliferation of new tests based on sophisticated technology has given impetus to critical evaluation of the role of clinical decision making. In this presentation selected aspects of ...

Assessment of antepartum cardiotocograms in high-risk pregnancy.

A ten-point scoring system was used to assess 2770 antepartum cardiotocograms (CTGs) obtained in 405 pregnancies at risk. There were 284 pregnancies with a last CTG within 24 hours before labour, Caesarean section or intrauterine death; these were analysed separately and their outcome correlated well with the last CTG score, better than with individual CTG criteria. The relationship between CTG score and fetal condition at birth was particularly close for pregnancies with growth retardation, rhesus isoimmunisation or hypertension. A score of 8 to 10 reliably predicted good condition at birth in 95 per cent of pregnancies which ended within 24 hours and in 88 per cent of those which ended after three or four days. A score of 5 points or less invariably indicated poor fetal condition with little chances of a normal outcome unless the cause could be effectively treated. The score provides a highly specific but moderately sensitive test for fetal well-being with virtually no false positive and only few false negative results. However, almost 15 per cent of CTGs, scoring 6 or 7 points, provide too little information on fetal well-being to be of clinical value.

Management of the pregnant, insulin-dependent diabetic woman.

An intensive care program was offered to all insulin-dependent, pregnant diabetic women who presented to The New York Hospital Obstetrical Clinic in their eighth week or less of gestation. The patients were hospitalized for 1 wk to normalize their blood glucose and to teach the technique of self-monitored glucose determination, diet and exchange lists, and the method to titrate insulin according to the blood glucose determination. The mean blood glucose for the first 10 patients accepted to the program was 169 mg/dl at the start of the program with a mean hemoglobin A1c of 9.4% for the group (normal < 5.5%) and glucosuria up to 50 g/24 h. After discharge, mean glucose was 91 mg/dl, and urinary glucose excretion was 1.4 g/24 h. HbA1c fell into the normal range 5 wk after normoglycemia was achieved (3.4%) (nl < 5.5%). Normoglycemia was maintained as outpatients until 3 wk before delivery when the patients were readmitted for tests of fetal well-being. Mean weight gain for the mothers was 12.2 kg. Mean glucose at delivery was 87 mg/dl and HbA1c was 3%. Hormonal profiles (hCG, hPRL, estrogens, progesterone, hPL) normalized after normoglycemia was achieved and remained normal until delivery. Mean gestational age at time of delivery was 38.8 wk with a mean infant birth weight of 2988 g. No infant manifested hypoglycemia, hypocalcemia, erythremia, or respiratory disease. The use of self-monitored blood glucose allows for optimal care of the insulin-dependent, pregnant diabetic woman while she remains at home with her family.

Fetal breathing movements and other tests of fetal wellbeing: a comparative evaluation.

Sixty pregnant women whose fetuses were considered to be at high risk were intensively studied with fetal and placental function tests. Fetal breathing movements were studied with real-time ultrasound and the amount of time spent breathing and the variability of the breath-to-breath interval were measured. A reduction in the amount of time the fetus spent making breathing movements and decreased variability were indicative of fetal compromise. When these results were compared with those of other tests of fetal wellbeing measurement of fetal breathing movements and ultrasound assessment of growth were more sensitive tests of fetal wellbeing than the biochemical measures (urinary oestrogen, human placental lactogen, pregnancy-specific beta-1-glycoprotein, and unconjugated oestriol concentrations) or fetal heart rate. The predictive value was highest with serum unconjugated oestriol but the results of other tests were similar. Study of fetal breathing movements or an ultrasonic assessment of growth may provide a better screening test for fetal compromise than biochemical estimations.

NORMAL PATTERNS OF FETAL ACTIVITY IN THE THIRD TRIMESTER

The incidence and frequency of fetal respiratory movements (FRM) and fetal trunk movements (FTM) were measured in 21 normal pregnancies between 28 and 39 weeks gestation. Fetal activity was assessed with a real-time ultrasound scanner and all observed movements were punched directly onto computer tape. Recordings were made for one hour in three over a 24 hour period, providing a total of 168 hours for analysis. The overall mean percentage incidence of FRM was 31 per cent at a mean breathing rate of 43 breaths/minute. The mean percentage incidence of FRM during the day (0800-1759 hours) was 37 per cent. The overall mean percentage incidence of FTM was 18 per cent with a mean of 29 moves per 30 minute observation period. The mean percentage incidence of FTM during the day (0800-1759 hours) was 16 per cent. There was a well-defined circadian variation in fetal activity with FRM peaking between 1900 and 2200 hours, and FTM between 2200 and 0100 hours. There was considerable variation in the amount of FRM and FTM recorded from hour to hour. Total fetal activity rarely fell below 10 per cent in any one recording period and this measurement may be a more useful clinical test of fetal well-being than FRM or FTM alone.

Some factors affecting the fetal heart rate

A phonocardiograph was used to investigate factors influencing fetal heart rate in utero. The use of this instrumentation is described. All data recorded were obtained by crude measurements of paper tapes or semiautomatically from magnetic tapes and a more sophisticated method of data reduction is presently being developed. Normal mothers were submitted to various stimuli to test their effect on maternal and fetal heart rate. The responses to inhalation of 100% and 12% oxygen were inconstant. There was no fetal response to administration of epinephrine or of norepinephrine. Atropine produced vagal blockade and tachycardia in both the mother and the fetus. There was a significant time dalay between the maternal and fetal response (e.g. Case 1 130 seconds for mother and 1290 seconds for fetus). This was of such duration as to allow time for the drug to cross the placenta and blockade the fetal vagus. Cigarette smoking produced fetal and maternal tachycardia. This response had a short time delay similar to that produced by fright. It may be caused by a reduction in uterine blood flow. It may be that accurate measurements of the parameters of such responses in normal and abnormal gravidas can serve as a test for fetal well-being and the adequacy of placental transfer.