Ultrasound measurement of the fetal head to abdomen circumference ratio in the assessment of growth retardation

Ultrasonic features of preeclampsia

Preeclampsia, the hypertension of pregnancy, is a high-risk obstetric situation that can be monitored ultrasonically. Ultrasonic features commonly associated with preeclampsia, including decreased total intrauterine volume (TIUV), oligohydramnios, and intrauterine growth retardation (IUGR), are presented and their possible prognostic implications discussed.

Comparative newborn anthropometric data in symmetric versus asymmetric intrauterine growth retardation

Autopsy studies have shown that the fetal liver is more severely affected than the brain in asymmetric fetal intrauterine growth retardation (IUGR). This "brain-sparing" concept has led to the suggestion that ultrasonic measurements of biparietal diameter (BPD) are of limited value in detecting IUGR since the BPD is an indirect reflection of head and brain size. This study compares the effects of asymmetric and symmetric IUGR on newborn anthropometric measurements, including head circumference (HC), birth weight (BW), length (L), and ponderal index (Pl) in 33 growth-retarded infants divided into two groups, asymmetric (uteroplacental failure) and symmetric (maternal smoking, drug exposure, congenital anomalies, intrauterine infection), on the basis of the etiology of the IUGR. The percentage reduction in size from mean values for the same gestational age was calculated for each parameter. None of the newborn parameters were useful in distinguishing between infants with asymmetric and those with symmetric IUGR. Particularly noteworthy is the fact that the percentage decrease in HC was similar in both groups. Therefore, the concept of absolute "brain sparing" in asymmetric IUGR is erroneous, and ultrasonic measurements of BPD should be of value in detecting this form of IUGR.

Hypervascularity of the uterine wall during pregnancy: incidence, sonographic appearance, and obstetric implications

The authors report the incidence (20%) of hypervascularity of the uterine wall (decidual reaction) (1) in 106 pregnant women studied prospectively by ultrasound. An unusual case, which caused problems in diagnosis and management, is reported in detail. The relation between the location and extent of this finding and the location of the placenta is discussed. The authors think that this finding represents dilation of myometrial veins of uncertain etiology, and they conclude that the major implications are that it must be differentiated from pathologic entities that are similar sonographically (1), and that if anterior, it may cause excessive bleeding during invasive procedures.

Screening for the small-for-dates fetus: a two-stage ultrasonic examination schedule

To find an effective routine screening method for small-for-dates fetuses 474 women with singleton pregnancies participated in a two-stage ultrasonic examination schedule. At the first-stage examination, which was conducted in early pregnancy, fetal crown-rump length or biparietal diameter was measured for an accurate assessment of gestational age, which was essential for interpreting the results of the second-stage examination. The second-stage examination was performed at 34-36 weeks and entailed measuring seven fetal variables, the results of which were assessed singly and in combination after delivery to identify the best indicator of small-for-dates fetuses. Fetal head measurements proved to be the least sensitive indicators of growth retardation, correctly identifying only 56-59% of cases. Measurements of trunk area and circumference, however, correctly identified 81% and 83% of cases respectively, but the most effective screening index was the product of crown-rump length and trunk area: with this index 34 out of 36 small-for-dates fetuses (94%) were correctly identified. Calculating the product of crown-rump length and trunk area from ultrasonic displays is quick and simple, and combined with the first-stage examination is a highly reliable screening method for small-for-dates fetuses.

Problems in ultrasonic monitoring of multiple pregnancies

Ultrasound would seem to be an ideal method of ensuring the early diagnosis of multiple pregnancy and also affords an opportunity to measure individual fetal growth thereafter. In a programme to study multiple pregnancies the majority were diagnosed early to allow adequate regular monitoring by ultrasound. Unexpected problems were encountered however and the failure rate to obtain satisfactory fetal biparietal measurements was almost three times that in singleton pregnancies.

Prenatal determination of fetal brain and somatic weight by ultrasound

A new method of determining fetal weight in utero is presented. Because it is based on multiple ultrasound measurements which encompass population and individual variations in fetal anthropometry, the method should be applicable to fetuses drawn from different populations. The components of fetal weight are separated into two variables, brain weight and somatic weight, which are independently determined. Their sum provides good estimates of total fetal weight in normal cases as well as those with asymmetrical growth retardation (Sy = 83 gm). The method generates the data required for interpreting fetal weight estimates in terms of any alteration in the brain:somatic weight relationship. It, therefore, yields quantitative information on the severity of asymmetrical IUGR.

An improved method of fetal weight estimation using ultrasound measurements of fetal abdominal circumference

A simple and accurate method is described for estimating fetal weight from a single fetal abdomen circumference measurement at the level of the umbilical vein. The abdominal circumference was converted into a weight centile for the maturity at the time of measurement so that the weight at delivery could be predicted. This method was tested on a population of fetuses presenting by the breech near term. Although the error between actual and predicted weights was 194 g (1 SD) for all the patients, for a large well-defined subgroup the error was much smaller, being only 104 g (1 SD).

Ultrasound assessment of fetal growth

Consecutive ultrasonic measurements of the fetal head area, thorax area, abdomen area, head/thorax (H/T) area ratio and head/abdomen (H/A) area ratio were obtained from 100 patients with a normal pregnancy and from 186 patients with suspected intrauterine fetal growth retardation. Of all the measurements used, H/A area ratio was found to be most accurate in identifying intrauterine fetal growth retardation predicting 82.9 per cent at 33 weeks and 85.7 per cent at 36 to 38 weeks of gestation. This technique was also found to be useful in distinguishing between the two types of growth retardation. The H/A area ratio was helpful in identifying the growth acceleration pattern of a large baby.

The value of diagnostic ultrasound as a screening test for intrauterine growth retardation: comparison of nine parameters

In an attempt to devise a screening method for the detection of unsuspected IUGR, a battery of ultrasonic measurements of the fetus were performed in a series of 255 patients at approximately 32, 34, and 36 weeks. The results obtained from the 16 growth-retarded and the 239 normally grown babies were evaluated. While no single measurement was found to discriminate the two groups, a simple combination of crown-rump length times area of trunk allowed us to identify an at-risk group comprising 11 per cent of the population. The false positive and false negative results were acceptable at levels of 10 and 6 per cent, approximately. It is considered that these results would justify a larger and prospectively randomized controlled trial to assess the benefits and drawbacks of applying these measurements in a screening schedule.

Comparison between subjective and ultrasound assessments of fetal movement

Forty pregnant women participated in a study to compare subjective with ultrasound assessments of fetal movements. A real-time ultrasound scanner was used. Movements were recorded for 45 minutes in all cases. There was a significant positive correlation between the number of movements recorded by the two methods, but the 95% confidence limits were wide and no correlation was found in those patients who recorded fewer than 20 movements in the study period. Thus "false-positive" information may be obtained from purely subjective data, and in patients reporting low "kick counts" fetal activity should be assessed from real-time ultrasound recordings.

The estimation of fetal weight by computer-assisted analysis

The need for a quick and easy method for estimating fetal weight in utero has been clearly established. Estimates by abdominal palpation and fetal hormone production have proved to be of limited value. Eight-five patients, ranging from 17 to 41 weeks' gestation, were ultrasonically scanned within 48 hours of delivery. Statistical analysis and multiple multivariant linear regressions were performed employing the BMD statistical packages. Our results show that birth weight is a logarithmic function of fetal body parameters and that the abdominal circumference has the single best correlation with the log10 birth weight. Our best linear regression with the use of two fetal dimensions (abdominal circumference and biparietal diameter) had a standard deviation of 106 grams per kilogram fetal weight. Since this derived formula is very cumbersome to manipulate, tables have been prepared with computer assistance to read the estimated fetal weight directly. Prospective estimates in 32 cases of both normal and pathologic gestations have proved to be within our expected accuracy.