Intrauterine volume, fetal abdominal area and biparietal diameter measurements with ultrasound in the prediction of small-for-dates babies in a high-risk obstetric population

Forty years of obstetric ultrasound 1957-1997: from A-scope to three dimensions

In this article, we record the history of obstetric ultrasound as it developed worldwide in the second half of the twentieth century. The technological advances during this period saw the evolution of equipment from the original adapted metal flaw detectors producing a simple A-scan to the modern, purpose built, real-time colour flow machines with three-dimensional capability (Fig. 1). Clinically, ultrasound began as a research tool, but the poor quality of the images led to the ridicule of many of the early investigators. However, because of their perseverance, ultrasound developed into an imaging modality providing immense diagnostic capabilities and facilitating with precision many invasive procedures, diagnostic and therapeutic, both of which have made significant contributions to patient care. In this history, we recall the people, the personalities, and the problems they encountered during the development of ultrasound and how these problems were resolved, so that ultrasound now is available for use in the care of pregnant women throughout the developed world.

Abnormal antenatal ultrasound findings and subsequent handicap

The modern ultrasound technique in its various modes, real-time B-mode, M-mode, continuous and pulsed wave Doppler ultrasound, makes it possible to study in detail the fetal anatomy and function in utero. Fetometry allows for the evaluation of fetal size and growth and for detecting growth-retarded or macrosomic fetuses. Ultrasound seems, at present, to be the best method available in the detection of the growth-retarded fetus who is at risk of developing perinatal complications and subsequent handicap. Ultrasound can also be used when fetal growth retardation is suspected on clinical grounds. An absolute prerequisite for the proper use of ultrasound fetometry is the estimation of gestational age in early pregnancy. The high resolution of modern ultrasound scanners allows the antenatal detection of even minor fetal structural abnormalities. When lethal malformations are detected early in pregnancy, selective termination of pregnancy can be considered. Fetal abnormality detected in late pregnancy allows for optimal timing and mode of delivery leading to improved management and outcome, thus lowering the risks of subsequent handicap. Ultrasound examination of the extrafetal structures, e.g. umbilical cord, placenta and amniotic fluid volume, may add valuable clinical information. The finding of severe oligohydramnios is associated with increased perinatal mortality and morbidity. Fetal circulation can be evaluated by using the combination of real-time and pulsed Doppler ultrasound or, alternatively, by employing continuous wave Doppler ultrasound alone. Pathological changes in the blood velocity waveforms recorded from the fetal and umbilical arteries may signify very early signs of fetal hypoxia. The method has the potential of becoming a useful clinical method for fetal surveillance. The guidelines for a proper application in the perinatal medicine of the Doppler method have, however, not yet been established. In fetuses with cardiac arrhythmia and/or cardiac malformation, the Doppler investigation of the fetal circulation can be used to evaluate the haemodynamic alterations and, in cases of intrauterine treatment, to supervise and monitor the therapeutic effects. Fetal motor function can be followed and quantified with real-time ultrasound. Abnormal motor activity might indicate bad perinatal outcome. The predictive capacity of the test is increased when several variables are combined (e.g. the fetal biophysical profile score).(ABSTRACT TRUNCATED AT 400 WORDS)

The clinical significance of Doppler umbilical artery velocimetry in the small for gestational age fetus

Fifty-four women who were delivered of small for gestational age infants were studied antenatally by serially continuous-wave Doppler velocimetry. Outcomes were compared in the normal and abnormal systolic/diastolic ratio groups. Seventy-eight percent had an abnormal systolic/diastolic ratio. The group with an elevated systolic/diastolic ratio had a significantly higher incidence of abnormal fetal heart rate, pregnancy-induced hypertension, oligohydramnios, cesarean section for fetal distress, and admission into the neonatal intensive care unit. One third of the newborns required intermittent positive pressure ventilation. Average birth weight and gestational age at delivery were significantly lower and there were six perinatal deaths in the group with an elevated systolic/diastolic ratio and none in the group with a normal systolic/diastolic ratio. These data suggest that the small for gestational age fetus with normal umbilical artery velocimetry is at significantly lower risk than are those with abnormal ratios. This implies that management of the small for gestational age fetus may now be aided by a functional classification based on the umbilical artery velocity waveform.

Diagnostic ultrasonography

The use of diagnostic ultrasound has contributed to the evaluation of the fetal condition in two ways--the detection of fetal abnormality and the assessment of fetal growth and development. Routine early pregnancy scanning enables most major structural anomalies to be detected and provides accurate gestational dating. Maternal serum alphafetoprotein screening complements ultrasound in identifying abnormalities, and may also be an indicator of a growth problem in later pregnancy. In high-risk pregnancies, or when growth retardation or acceleration is suspected, abnormalities should always be considered and investigations should include karyotyping. Fetal growth may be assessed by multiple parameters, including measurement of fetal head, trunk, limbs, and amniotic fluid volume, in addition to grading of the placenta. Fetal responses to stimulation can be visualized and quantified. No single parameter may be used alone to predict fetal outcome, but by using this multiple-parameter approach, contributing to a biophysical profile of the fetus, the outcome of pregnancy may be predicted with greater accuracy.