Estimation of fetal weighty by ultrasonic abdominometry

Correlation of Ultrasonographic Estimation of Fetal Weight with Actual Birth Weight as Seen in a Private Specialist Hospital in South East Nigeria

Background

Ultrasound estimation of fetal weight at term provides vital information for the skilled birth attendants to make decisions on the possible best route of delivery of the fetus. This is more pertinent in a setting where women book late for antenatal care.

Aim and Objectives

The study evaluated the accuracy of estimation of fetal weight with ultrasound machine at term.

Methods

This was a cross sectional study conducted at a private specialist hospital in Nigeria. A coded questionnaire was used to retrieve relevant information which included the last menstrual period, gestational age, parity, and birth weight. Other information obtained includes Ultrasound-delivery interval, maternal weight, and route of delivery. The ultrasound was used to estimate the fetal weight. The actual birth weight was determined using a digital baby weighing scale. The data were inputted into Microsoft excel and analyzed using STATA version 14. Statistical significance was considered at p-values less than 0.05. Measures of accuracy evaluated in the statistical analysis included mean error, mean absolute error, mean percentage error, and mean absolute percentage error. Pearson correlation was done between the estimated ultrasound fetal weight and the actual birth weight. The proportion of estimates within ±10% of actual birth weight was also determined.

Result

A total of 170 pregnant women participated in the study. The mean maternal age was 30.77 years ± 5.54. The mean birth weight was 3.47 kg ± 0.47, while the mean estimated ultrasound weight was 3.43 kg ± 0.8. There was positive correlation between the ultrasound estimated weight and the actual birth weight. The mean ultrasound scan to delivery interval was 0.8 days (with range of 0–2 days). The study recorded a mean error of estimation of 41.17 grams and mean absolute error of 258.22 grams. The mean percentage error was 0.65%, while the mean absolute error of estimation was 7.56%. About 72.54% of the estimated weights were within 10% of the actual birth weight.

Conclusion

The ultrasound estimated fetal weight correlated with the actual birth weight. Ultrasound estimation of fetal weight should be done when indicated to aid the clinician in making decisions concerning routes of delivery.

Characteristics of monochorionic-diamniotic growth-retarded twins during the third trimester

The goal of this study was to assess the characteristics of monochorionic-diamniotic (MD) growth-retarded twin infants with twin-twin transfusion syndrome (TTTS) compared with those without TTTS during the third trimester. Retrospective analyses of the growth patterns and amniotic fluid volumes were performed on 5 MD twin pregnancies in which one or both twins showed growth retardation with TTTS, and the results weve compared with those without TTTS. Eighty-three percent of growth-retarded twin infants without TTTS in MD twin gestation showed an asymmetric growth pattern, while all TTTS cases showed a symmetric pattern (p < 0.05). Polyhydramnios of the co-twin was found in 80% of TTTS cases, while no polyhydramnios was found in patients without TTTS (p < 0.05). Assessment of growth patterns and amniotic fluid volume may be useful to exclude the possibility of TTTS in MD growth-retarded twin pregnancies during the third trimester.

Prediction of birth weight using the Rossavik growth model: a study in a Dutch population

OBJECTIVES

To evaluate the Rossavik growth model for predicting birth weight in a Dutch population and to evaluate growth cessation near term.

STUDY DESIGN

Birth weight was predicted at various ages between 38 and 42 weeks, menstrual age (MA), and at birth age in 50 normal infants using two sets of ultrasound measurements obtained before 28 weeks, MA. Predicted birth weights were compared to actual weights. The mean percentage difference was used as a measure of systematic error and the standard deviation as a measure of random error. Linear regression analysis was used to evaluate the relationship between percentage differences and birth age. To evaluate the individual growth potential, the Growth Potential Realization Index for weight (GPRIWT) was determined for each fetus.

RESULTS

The predictions at 39 and 39.15 weeks, MA, were accurate without systematic error and with a random error of +/-9.3%. Prediction at 38 weeks showed a statistical underestimation (mean +/- SD = -5.8% +/- 8.8), and statistical overestimations were found for predictions after 39.15 weeks and at birth age. A relationship between percentage differences and birth age was not found for predictions between 39.15 and 40 weeks, MA. These findings indicate that growth cessation occurred at 39.15 weeks, MA. Using birth weights predicted at 39.15 weeks, MA, GPRIWT were calculated. The mean GPRIWT value was not significantly different from 100% (p > 0.05), and individual GPRIWT values ranged from 84% to 114%.

CONCLUSIONS

The Rossavik growth model can be used to predict birth weight in a Dutch population. However, growth cessation near term appears to occur later than previously reported in other populations.

Fetal growth velocity: kinetic, clinical, and biological aspects

With the aim of determining fetal growth kinetics, prenatal data were analysed which had been longitudinally collected in the framework of a perinatal growth survey. The sample comprised 238 singleton normal pregnancies, selected in Genoa and Turin (between 1987 and 1990), and repeatedly assessed by ultrasound scans (five to nine per pregnancy). Five morphometric traits were considered: BPD (biparietal diameter), OFD (occipitofrontal diameter), HC (head circumference), FDL (femur diaphysis length) and AC (abdomen circumference). Growth rate seemed to increase in the early part of the second trimester, and decrease subsequently: velocity peaks were steeper and earlier for head diameters and circumference (about 18 weeks) than for femur length (20 weeks) and abdomen circumference (22 weeks). Velocity standards were traced using a longitudinal two-stage linear model: this ensures unbiased description of the shape of the growth curve, even when growth kinetics are asynchronous, and efficient estimation of the outer centiles--the most useful for diagnostic purposes.

Longitudinal follow-up of 100 patients at risk of intrauterine growth retardation: comparison of diagnosis in two periods

The concept of low birth weight includes two different entities: prematurity and intrauterine growth retardation. Both of them are major public health problems, because they increase perinatal morbidity and mortality Early diagnosis of IUGR leads to adequate decisions, making possible a reduction in perinatal morbidity and mortality. In order to make an early diagnosis of IUGR, clinical methods have proven to be insufficient. Ultrasonography is an important aid to this diagnosis, introducing the measurement of fetal diameters and perimeters. This study, designed to compare both methods, was carried out in at the Antoine Béclère Hospital, Clamart, France. Data processing was done in CLAP-PAHO/WHO. In the first period, retrospective analyses of 116 clinical histories with IUGR were performed. In this study, only fetal diameters were used and the accuracy of clinical and ultrasonographic diagnosis was evaluated. In the second period a prospective longitudinal follow-up study of 100 pregnant women at risk of developing IUGR was carried out. Clinical diagnosis was also evaluated, and compared to the ultrasonographic approach. The parameters used were the fetal diameters and perimeters (head and abdominal perimeters, and their relationship). Sensitivity, specificity and predictive values of the ultrasonic parameters were calculated (table I). The clinical and ultrasonographic diagnosis of both periods were compared with the purpose to analyze the effect of the measurement of fetal perimeters in the diagnostic accuracy. Newborns of the 100 patients in the prospective study were classified into two groups according to birth weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Infantile polycystic kidney disease: observations from attempts at prenatal diagnosis

Three successive pregnancies of a couple at risk for infantile polycystic kidney disease were evaluated by sequential ultrasound examinations to attempt prenatal diagnosis of the disorder. The gestational age at which renal sonographic changes were noted varied from 20 to 34 weeks and resulted in both false-positive and false-negative diagnoses.

Introduction to the study of pre- and postnatal growth in humans: a review

This review is divided in several items. A brief introduction on the characterization of the growth processes is made; the ways of assessing fetal development and well-being, the factors acting on fetal growth and birth weight, the causes and post-natal consequences of prematurity and intrauterine growth retardation are discussed in the first part. The following items deal mainly with: the normal pattern of growth from birth to puberty according to sex, race, and nutritional status, with special mention to pubertal changes; methods for predicting adult height from skeletal age; the effect of hormones during pre- and post-natal life; and the genetics of adult stature. The remainder of this review deals with genetic causes of growth abnormalities. Constitutional delay of growth, familial short stature, hypothalamic-pituitary dwarfism, skeletal dysplasias and many genetic syndromes presenting intrauterine growth retardation are listed. Aneuploidy effects on human growth are extensively reviewed, and usual growth patterns in Down and Ullrich-Turner syndrome patients as well as other sex aneuploid individuals and mosaics are fully described. The influences of X and Y chromosomes on growth and maturation are also discussed. Finally, some remarks are made about overgrowth syndromes.

Mathematical modeling of fetal growth: II. Head cube (A), abdominal cube (B) and their ratio (A/B)

Growth of the fetal head and abdomen have been monitored by measurement of the head cube (A), the abdominal cube (B) and A/B, from 12 to 41 weeks menstrual age. Growth curves for these parameters have been determined using a specially developed growth curve model [P = c(t)k+s(t)]. R2 values of 98.0%, 96.6%, and 56.2% were obtained for A, B, and A/B, respectively. Similar results were obtained when this model was used with HC and AC data from a previous study. Variability analysis indicated a progressive increase in variability with menstrual age for both A and B while the variability of A/B decreased. The variability in the 12- to 17-week interval was significantly greater for all three parameters and the A deviation distribution was asymmetric (shifted toward negative values) after 36 weeks. Variability data were used with the growth curve models to determine standard curves for A, B and A/B.

Diminished growth in fetuses born preterm after spontaneous labor or rupture of membranes

We examined biparietal diameter, abdominal circumference, and birth weight in 148 preterm infants to assess fetal growth. A statistically significant proportion of preterm fetuses had biparietal diameter and abdominal circumference values below the fiftieth and tenth percentile levels as compared with that expected in normal fetuses. Similarly, birth weight of infants in the study fell significantly below the fiftieth and tenth percentiles relative to Brenner's curve. We conclude that diminished fetal growth is associated with early delivery secondary to preterm labor or preterm premature rupture of membranes or both. Additionally, since biparietal diameters in preterm fetuses are smaller than those of normal fetuses the prediction of gestational age by cephalometry should be advanced by 7 to 10 days.

A simple estimated fetal weight equation based on real-time ultrasound measurements of fetuses less than thirty-four weeks' gestation

Based on ultrasonographic mensuration, a number of equations have previously been devised for the purpose of estimating fetal weights. The objective of this study was to develop a mathematical equation that is simple, accurate, and easy to use when applied to preterm or low-birth weight fetuses (less than 2,500 gm). Real-time ultrasound measurements of fetal biparietal diameters (BPDs) and abdominal circumferences (ACs) were obtained in 62 pregnant women within one week of premature delivery. Mean gestational age and mean birth weight +/- SD for this study group of neonates were 28.5 +/- 3.5 weeks and 1,135 +/- 343 gm, respectively. With the aid of computer analysis, a simple regression equation was derived: EFW = (BPD x AC x 9.337) - 229. When predicted estimated fetal weight (EFW) was compared with actual birth weight (ABW), multiple regression analysis demonstrated a correlation coefficient (R) of 0.957. Preliminary results on 19 patients of a prospective study showed an absolute mean difference between the computed EFWs and the ABWs to be within 7.0% of ABW (70 gm/kg of ABW). The standard deviation of the difference was 9.3% of ABW (93 gm/kg of ABW). Based on these data, this simple equation appears to be clinically reliable and easy to use when estimating weights of preterm or low-birth weight fetuses of less than 2,500 gm.

Ultrasonic patterns of intrauterine fetal growth in a Latin American country

Head circumference and its cross-sectional area, biparietal and fronto-occipital diameters, abdominal circumference and its cross-sectional area, and the transverse and anteroposterior diameters were measured in 30 healthy single fetuses from normal pregnancies by means of ultrasound. The 5th, 50th and 95th percentiles of distance and velocity curves are described. The comparison of the values of a perimeter (abdominal or cephalic) measured directly from the photograph or calculated by the ellipse formula, showed a straight correlation. The use of the ellipse formula in current practice may simplify and reduce the cost of this technology.

The prenatal determination of fetal weight by dynamic scanning

An equation based on ultrasound measurements to estimate fetal weight must reflect the relationships between parameters of fetal size and growth as well as the change in fetal shape which occurs in relation to varying nutritional supplies. Four equations have been compared with respect to these demands. The material was collected from everyday practice in our hospital. Good results were obtained using two of the equations, and it was suggested that they may serve as valuable tools in studies of fetal growth.

An evaluation of two methods of antenatal ultrasonic fetal weight estimation

The accuracy of 2 methods of antenatal ultrasonic fetal weight estimation has been compared. The method of Warsof et al. (1977) computes the estimated fetal weight from measurements of the abdominal circumference and the biparietal diameter, whilst the method of Higginbottom et al. (1975) utilises the circumference of the abdomen alone. The estimated weights obtained by the 2 methods were compared with the actual weights at birth occurring within 48 hours of the estimation. Using the tables of Warsof et al., 77% of the actual birth weights were within 10% of the estimated weight, with a coefficient of correlation of 0.95. Eighty-two per cent of babies less than 2,500 g fell within 10% of the estimated weight (Warsof et al.), with a coefficient of correlation of 0.96. Using the formula of Higginbottom et al., 56% of the total birth weights fell within 10% of the estimated weight and the coefficient of correlation was 0.89. Forty-five per cent. of the babies weighing less than 2,500 g were within the 10% range, the coefficient of correlation of this subgroup being 0.91. It is concluded that antenatal fetal weight estimation using the computed tables of Warsof et al. is superior in our population to the method described by Higginbottom et al., and such antenatal fetal weight estimation is of potential value in many high risk pregnancies.

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.

Estimation of fetal weight from ultrasonic measurements

Ultrasonic measurements were made on 65 fetuses within 48 hours of delivery. Multiple regression analysis of birth weight and the natural logarithm of birth weight against several measured variables were obtained. The formula giving the best correlation was a polynomial regression of the natural logarithm of birth weight vs. trunk circumference, circumference, and a long axis measurement. The correlation was improved by excluding the first 15 patients but was not improved further by excluding the next 15. The best correlation was 0.944, giving a predicted birth weight error of +/- 103 Gm. (1 S.D.).