A pilot study of time allocation and reimbursement for routine obstetric ultrasonography.

OBJECTIVE: To evaluate time allocation during initial and repeated ultrasonography and to formulate recommendations to improve unit efficiency. METHODS: Over a 2-year period, 51 comprehensive ultrasonographic examinations between 14 and 38 weeks' gestational age were observed by a single reviewer. Each patient-sonographer interaction was divided into timed segments, including setup, examination time, review, and turnover. Statistical analysis using descriptive statistics, Student ttest, and analysis of variance was performed to determine the effect of the number of ultrasonographic examinations, sonographer experience, estimated gestational age, and patient body mass index on examination time. RESULTS: The average time spent with each patient was 15 minutes 22 seconds: 2 minutes 10 seconds for setup, 9 minutes 38 seconds for examination, 1 minute 50 seconds for review, and 1 minute 44 seconds for turnover. Examination length was not significantly affected by estimated gestational age, body mass index, ultrasonography experience, or the number of ultrasonographic examinations (P > .05). No statistical significance in the duration of scanning was found between initial (15 minutes 3 seconds) and repeated (16 minutes 1 second) examinations (P = .609). Nonexamination activities, such as data entry and room cleanup, consumed 37% of the sonographer's time. CONCLUSIONS: Resource use within the ultrasonography department may be improved by reassigning clerical and custodial duties from sonographers to other personnel. Although differential reimbursement exists, no statistically significant difference in resource use between initial and repeated examinations was found.

Correctly identifying the macrosomic fetus: improving ultrasonography-based prediction.

OBJECTIVE: Our goal was to improve the accuracy of estimating fetal weights among macrosomic fetuses with the traditional measurements of abdominal circumference, femur length, and head circumference. STUDY DESIGN: We used 4831 cases without anomalies from an ultrasonography laboratory database with an estimated fetal weight obtained a maximum of 14 days before delivery. Abdominal circumference, femur length, and head circumference were each regressed on birth weight to obtain estimated fetal weight by abdominal circumference, femur length, and head circumference, respectively. We compared the individual variation for estimated fetal weight by abdominal circumference, femur length, and head circumference by calculating a within-subject standard deviation to quantify the level of disparity. We adjusted the estimated fetal weight to the date of delivery and for dependencies on maternal diabetes mellitus, weight, and height. We then weighted cases with birth weight >4500 g and diabetic cases with birth weight >4000 g 20-fold (weighted estimated fetal weight) for the purpose of creating a favorable bias for classifying these cases. The equation of Hadlock et al, with abdominal circumference, femur length, and head circumference, was applied as a benchmark estimated fetal weight. RESULTS: Of the 4831 newborns, 308 (6.4%) had a birth weight >4000 g, and 56 (1.2%) had a birth weight >4500 g. There were 154 pregnancies complicated by diabetes mellitus; 26 (16.9%) of the resulting infants weighed >4000 g, and 5 (3.2%) weighed >4500 g. At 95% specificity, the weighted estimated fetal weight had a sensitivity of 85.7% at a cut point of 3912 g, compared with a sensitivity of 71.4% at 3604 g by use of the estimated fetal weight of Hadlock et al. CONCLUSIONS: We were able to improve the accuracy of identifying the macrosomic fetus compared to reliance on the equation by Hadlock et al. A fetus was found to be at significantly increased risk for birth weight >4000 g when the estimated fetal weight based on abdominal circumference is larger than that based on either head circumference or femur length or when there is a large within-subject variance in estimated fetal weight based on abdominal circumference, femur length, and head circumference. We also found that there were significantly different groups of patients whose estimated fetal weights require different equations for better estimates. Even given ultrasonographic measurements, taking into account maternal height, weight, and presence of diabetes mellitus can improve macrosomia detection. Although these findings remain to be optimized and validated, the approach used here appears to yield better predictions than the current "one function fits all" approach.

Telemedicine and fetal ultrasonography: assessment of technical performance and clinical feasibility.

OBJECTIVE: Our aim was to determine the performance and clinical feasibility of telesonography for the interpretation of fetal anatomic scans sent from a remote location compared with those obtained at a tertiary care prenatal ultrasonography center. STUDY DESIGN: Routine ultrasonographic studies from 35 patients were remotely interpreted. Evaluation included a blinded comparison of the sonographer's assessment of 38 fetal structures with that of the physician at the tertiary care center. Technical evaluation included system reliability and the number of digital telephone lines required for adequate real-time visualization. RESULTS: The mean gestational age at the time of the ultrasonography was 25.84 +/- 6.8 weeks (range 14 to 38). There was complete consistency of interpretation for 25 of 38 (66%) fetal structures. Thirteen structures had discrepancies in visualization, reflecting a difference in the adequacy of visualization, not the normalcy or identity of the structures. Three digital (integrated switching digital network, ISDN) telephone lines were required for real-time visualization. CONCLUSION: Our preliminary experience supports telesonography as a clinically useful tool for remote interpretation of fetal ultrasonographic examinations. Further studies are warranted for the continued evaluation of this emerging technology.

Integration of genetics and ultrasonography in prenatal diagnosis: just looking is not enough.

OBJECTIVE: There has been a gradual shift of the focus of prenatal diagnosis from genetics to ultrasonography. We assessed our primary genetics approach to determine what would be missed without the genetics component. STUDY DESIGN: We evaluated referral indications for patients with normal and abnormal prenatal findings from Jan. 1, 1990, to March 31, 1995, and categorized them according to type of fetal anomalies and genetic abnormalities found. Discordance among initial indication, identified risk factors, and observed abnormalities was assessed. RESULTS: The proportion of patients referred for very-high-risk indications increased over time; 13.5% of all patients (1992 of 14,725) had abnormalities. Abnormal outcomes were categorized as 26% chromosomal, 58% ultrasonographic dysmorphologic features, 11% biochemical or deoxyribonucleic acid disorders, 5% infectious, and 11% other. Of the cases of ultrasonographic dysmorphism (exclusive of the aneuploidies), 3.5% were ultimately determined to be syndromic and 2.5% to be discrepant, that is, having a different abnormality than the referred diagnosis. Including the whole spectrum of disorders seen, half of the abnormalities would not be detectable with even high-quality ultrasonography. CONCLUSION: A large number of abnormal findings were not consistent with initial indication for referral. Correct diagnosis depended on increased acuity provided by genetic pedigree analysis and recognition of syndromes. Diligence in the search for associated anomalies, aneuploidy, pedigree analysis, and syndromic abnormalities remain critical components in the differential diagnosis. The elucidation of unexpected findings suggests the advantages of early counseling and a genetics-based approach combined with tertiary rather than primary ultrasonography with counseling only when anomalies are detected.

International, collaborative experience of 1789 patients having multifetal pregnancy reduction: a plateauing of risks and outcomes.

OBJECTIVE: To develop the most up-to-date, complete data base of multifetal pregnancy reduction (MFPR) from cases, and to provide the best counseling for couples with multifetal pregnancies. METHODS: From nine centers in five countries, 1789 completed MFPR cases were collected and outcomes evaluated. Pregnancy losses were defined as through 24 weeks and deliveries categorized in groups of 25-28, 29-32, 33-36, and 37 or more weeks. RESULTS: Overall, the pregnancy loss rate was 11.7% but varied from a low of 7.6% for triplets to twins and increased with each additional starting number to 22.9% for sextuplets or higher. Early premature deliveries (25-28 weeks) were 4.5% and varied with starting number. Loss rates by finishing number were highest for triplets and lowest for twins, but gestational age at delivery was highest for singletons. CONCLUSIONS: Multifetal pregnancy reduction has been shown to be a safe and effective method to improve outcome in multifetal pregnancies. Outcomes are worse with higher-order gestations and support the need for continued vigilance of fertility therapy.

Centile-based ultrasound morphometric tables.

Current ultrasound morphometric tables estimate centiles assuming normal distribution and similar variation throughout gestation. Our goal was to develop normative tables for biparietal diameter, femur length and average abdominal diameter using actual centiles. We studied the last complete ultrasound examination from 9510 singleton, live pregnancies without major malformations delivered at our hospital. Actual 5th, 10th, 50th, 90th and 95th centiles were calculated for each week and compared to estimates based on means and standard deviations. With advancing gestational age, variation in average abdominal diameter increased and variation in biparietal diameter and femur length remained stable. The largest difference between an actual and an estimated centile limit was 2 mm for biparietal diameter or femur length and 3 mm for average abdominal diameter. Differences between true and estimated centile limits were less than the intraobserver variation of the ultrasound measurements and therefore clinically unimportant.

Transabdominal versus transcervical and transvaginal multifetal pregnancy reduction: international collaborative experience of more than one thousand cases.

OBJECTIVES: Two major approaches for multifetal pregnancy reduction have been developed over the past several years: transabdominal potassium chloride by injection and pelvic procedures by either transcervical aspiration or transvaginal potassium chloride injection or by an automated spring-loaded puncture device. The purpose of this study was to create the largest database from among the world's largest centers to assess possible differences in efficacy and complication rates by transabdominal or transcervical or multifetal pregnancy reduction. STUDY DESIGN: Data on over 1000 completed pregnancies that underwent multifetal pregnancy reduction by both methods from major centers with among the highest worldwide experience were combined. Transabdominal cases were divided temporally (1986 through 1991 and 1991 through 1993). RESULTS: Transabdominal multifetal pregnancy reduction was successfully performed on 846 patients and transcervical or transvaginal on 238 patients. Transcervical or transvaginal reduction is performed earlier and starts and finishes with fewer embryos. In 12.6% of cases transcervical or transvaginal reduction left a singleton as opposed to 4.4% for transabdominal reduction. Pregnancy losses (up to 24 weeks) were observed in 13.1% of transcervical or transvaginal cases and in 16.2% of transabdominal cases early in the series and 8.8% of late transabdominal cases. Transcervical or transvaginal reduction may be safer very early in gestation and transabdominal safer later in the first trimester. Premature deliveries were comparable, with only about 5% delivered between 25 and 28 weeks. The smaller starting numbers for transcervical and transvaginal reduction may explain a slightly higher term delivery rate. The transabdominal route tends to reduce the fundal embryos and the transcervical and transvaginal the lower ones. The significance of this is not clear. CONCLUSIONS: (1) Multifetal pregnancy reduction by either method is a relatively safe and efficient method for improving outcome in multifetal pregnancies. (2) More than 84% are delivered at > 33 weeks. (3) The experience and preference of the operator are probably the key determinants for an individual patient. (4) An inverse relationship of starting and finishing number to loss rates and gestational age at delivery suggests that there still is a cost of iatrogenic multifetal pregnancies, even if multifetal pregnancy reduction can be successfully performed.

Ultrasound-detected free-floating particles in amniotic fluid: correlation with maternal serum alpha-fetoprotein.

The objective of this study was to determine the rate of ultrasound-detected free-floating particles in amniotic fluid during the early second trimester and their relationship with maternal serum alpha-fetoprotein (MSAFP) in patients with normal amniotic fluid alpha-fetoprotein (AFAFP). Ninety-eight consecutive patients undergoing second-trimester amniocentesis for various indications were prospectively studied. Before undergoing amniocentesis, each patient had a level II ultrasound examination and evaluation of the presence of free-floating particles. A subjective estimate of the particle amount and measurement of the size of the largest particle seen were made. Patients were stratified into three groups according to their MSAFP level (low, normal, high). Statistical significance of results was assessed by analysis of variance and multiple comparison procedure, and by nonparametric procedures, as appropriate. MSAFPs (mean +/- 1 SD) were 0.41 +/- 0.18 and 4.88 +/- 2.22 multiples of the median for the low and the high groups, respectively. All AFAFPs were within normal limits. Ninety-four percent of patients with high MSAFP had free-floating particles in amniotic fluid as compared to 43% in the low and normal groups (p < 0.01). Patients with high MSAFP had significantly greater density and size of particles. The presence of ultrasound-detected free-floating particles in amniotic fluid of normal patients during the early second trimester may preclude its use as a reliable indicator for fetal lung maturity, or suggest that the source of these particles may differ by trimester. High MSAFP is significantly correlated with the ultrasonographic appearance of free-floating particles, as well as with larger size and higher amount.

Single umbilical artery: accurate diagnosis?

OBJECTIVE: We sought to evaluate the accuracy of ultrasonographic, obstetric, and neonatal diagnosis of a single umbilical artery. STUDY DESIGN: We studied 17,777 consecutive singleton births from women who had undergone ultrasonographic examination at our hospital. A single umbilical artery was confirmed in 37 cases (0.2%) by two clinical methods or by pathologic assessment. Outcome of neonates with a single umbilical artery was compared with the outcome of neonates with either two or three vessel cords. RESULTS: Ultrasonographic diagnosis had a 65% sensitivity and positive predictive value. Obstetricians and pediatricians failed to diagnose 24% and 16% of the cases, respectively. On average, neonates with a single umbilical artery weighed 320 gm less, were delivered 1 week earlier, and had lower Apgar scores than neonates with three vessel cords (p < 0.01 in each case.) CONCLUSION: Although early gestational age may account for some cases not diagnosed by ultrasonography, there is a little justification for missing the diagnosis after delivery. Greater emphasis on clinical examination of the umbilical cord is needed to identify neonates at risk of associated malformations.

Efficacy of transabdominal multifetal pregnancy reduction: collaborative experience among the world's largest centers.

OBJECTIVE: To evaluate the safety and efficacy of transabdominal multifetal pregnancy reduction (MFPR) in the management of iatrogenic and spontaneous multifetal pregnancies. METHODS: Data were combined from 463 completed pregnancies that underwent MFPR at major worldwide centers. RESULTS: Multifetal pregnancy reduction was performed with a 100% technical success rate (there were no failed procedures); 83.8% had delivery of potentially viable fetuses (defined as 24 weeks' gestation or later), and 83.5% of these viable pregnancies delivered at 33 weeks or later. The risk of fetal loss was 3.9% at 2 weeks or less post-procedure, 4.6% at 4 weeks or less, and 16.2% at less than 24 weeks of gestation. Gestational age at delivery varied principally with the number of fetuses remaining, with 7.1% delivering prematurely at less than 28 weeks, and 9.4% at 29-32 weeks. The incidence of obstetric and medical complications appeared to be unaffected, and there was no increase in congenital malformations. CONCLUSIONS: Multifetal pregnancy reduction is an efficient and safe way of improving outcome in multifetal pregnancies, unambiguously for quadruplets or more, and arguably for triplets. However, particularly at higher starting numbers, there are still suboptimal outcomes. We cannot answer the question of whether MFPR should be offered to women with triplets or twins. The only major risk appears to be fetal loss per se, and because the procedure itself does not damage the survivors, parental autonomy should be given a higher priority in the decision process than previously. However, to obviate the need for this procedure, infertility specialists must continue to be vigilant in the use of fertility drugs.

Trends in sonographic fetal organ visualization.

In order to assess changes in sonographic visualization over the last 6 years, 7092 second- and third-trimester ultrasound examinations from separate pregnancies in three individual years (1451 in 1985, 3016 in 1988, and 2625 in 1991) were compared. Overall, visualization across all gestational ages improved from 63.9% (1985) to 85.8% (1988) to 87.3% (1991), with the year in which the scan was performed explaining 19.6% of the variance in visualization. Maternal size (as determined by body mass index) remained the major determinant of ultrasound visualization in 1991 (r(2) = 11.2%), with gestational age explaining only 5.2% additional variance. Overall organ visualization was maximal at 21-23 weeks' gestation, with the decline in later gestation primarily accounted for by worsened visualization of fetal extremities and spine. Improved fetal visualization earlier in the second trimester and the advent of embryonic visualization in the first trimester may allow a continuum of prenatal sonographic diagnosis.

The smaller than expected first-trimester fetus is at increased risk for chromosome anomalies.

OBJECTIVE: Intrauterine growth retardation associated with fetal chromosome anomalies is usually documented on ultrasonography late in the second trimester. However, we believe and attempt to document here that the impact of aneuploidy on fetal growth is evident much earlier (i.e., the aneuploid fetus may appear smaller than dates on ultrasonography even in the first trimester). STUDY DESIGN: For the population referred to our center for chorionic villus sampling from January 1988 to July 1991, we compared gestational age as calculated from the last menstrual period to that derived from fetal size as measured by crown-rump length. A cutoff of 7 days was chosen to select the study group. The remainder of our chorionic villus sampling population in which fetal size was expected was used as controls. We also divided those chorionic villus sampling patients by when a fetal death was observed by size. RESULTS: In the study period 3194 chorionic villus sampling procedures were performed and in 277 (8.7%) fetal length was smaller than expected by at least 7 days. Sixty (1.9%) chromosome anomalies were diagnosed by first trimester chorionic villus sampling in the study period. The frequency of chromosome anomalies was 4.3% in the study group and 1.7% in controls (p < 0.004). The more aberrant the karyotype on "postmortem chorionic villus sampling," the greater the growth retardation tended to be. CONCLUSIONS: In our chorionic villus sampling population a fetal crown-rump length smaller than dates is associated with a significant increase in risk of chromosome anomalies. Moreover, the larger the size-dates discrepancy, the higher the possibility that the aneuploidy affecting that pregnancy is of the severe or lethal type.

Chorionic villus sampling: transabdominal versus transcervical approach in more than 4000 cases.

OBJECTIVE: To address the evolving trends in the choice of transabdominal or transcervical chorionic villus sampling (CVS) at a teaching hospital and to evaluate the influence of gestational age on the approach chosen. METHODS: We analyzed our CVS data base, which contained information from 1986-1991. The proportions of transabdominal and transcervical CVS were tabulated for each year. In addition, the distribution of the CVS approaches over the various gestational ages was examined. RESULTS: During the study period, 4290 CVS procedures were performed. The rate of the transabdominal technique was stable at about 15% per year except for the first 2 years, when essentially all procedures were transcervical. Use of transabdominal CVS increased with advancing gestational age, from 3.6% at less than 10 weeks' gestation to 97.6% at greater than 14 weeks (chi 2 = 120, P less than .001; r = 0.791). CONCLUSIONS: The choice between the transabdominal and transcervical approach to CVS largely reflects the route emphasized during the physician's training. When choice is based strictly on technical limitations due to placental position, the overall transabdominal CVS rate is approximately 15%. A shift from transcervical to transabdominal CVS occurs with increasing gestational age as the placenta gains bulk and moves away from the cervix. After 14 weeks' gestation, most procedures are performed transabdominally.

Biparietal diameter and femur length discrepancies: are maternal characteristics important?

We examined whether gestational age, maternal race or height can be used to explain discrepancies between biparietal diameter- and femur length-derived gestational ages by analyzing ultrasound scans from 8041 consecutively scanned, singleton pregnancies, using multiple regression analysis. While a consistent association was noted between differences of more than 3 weeks and less than 3 weeks and advancing gestational age, neither maternal height nor race were significantly related. We conclude that, first, discrepancies between gestational age by biparietal diameter and femur length are rare (5%) and, second, the presence of discrepancies should not be dismissed on the basis of maternal stature or race and should alert the clinician to possible abnormal fetal growth or development.

Postmortem chorionic villus sampling: correlation of cytogenetic and ultrasound findings.

We performed chorionic villus samplings (CVS) in 795 cases in the first trimester during a 13-month period. Of these 35 were found to have a blighted ovum or missed abortion prior to the procedure. Nineteen women consented to have CVS. Ultrasonographic and cytogenetic findings in these 19 pregnancies were correlated. Expected gestational age was determined by last menstrual period. Observed gestational age was determined by crown rump length (CRL) (12 pregnancies) or gestational sac (GS) (7 pregnancies without fetal pole). The differences in days between the estimated and observed gestational ages was determined for each pregnancy. In all 19 CVS samples cytogenetic diagnosis documented aneuploidy. Ten cases had chromosome abnormalities virtually always lethal in the embryonic period (group I). Nine pregnancies had defects with moderate potential for fetal viability (group II). Gestations with low viability potential (group I) had estimated minus observed gestational age discrepancies (23.4 +/- 8.3 days) significantly greater than gestations with moderate viability potential (group II) (8.9 +/- 4.3 days) (P less than .001). The absence of a fetal pole was more common in group I. CVS in pregnancies with missed abortion or blighted ovum is feasible and has a high likelihood of documenting aneuploidy. Furthermore, the more severe the anomaly the more likely there will be very early fetal demise or intrauterine growth retardation.

The clinical utility of maternal body mass index in pregnancy.

To describe maternal body mass index and to compare the use of maternal weight and body mass index for risk assessment at the initial prenatal visit, 6270 gravid women who were consecutively delivered of infants were studied. Body mass index increased with advancing maternal age, parity, and advancing gestational age and was significantly greater in black women than in nonblack women. Risks for the development of adverse outcome associated with maternal obesity, including development of gestational diabetes, preeclampsia, fetal macrosomia, and shoulder dystocia, were comparably predicted by either maternal weight or body mass index greater than 90th percentile. Maternal weight was as predictive of preeclampsia, macrosomia, and shoulder dystocia as was body mass index when these factors were analyzed as continuous variables, whereas increasing body mass index was more predictive of gestational diabetes. The prediction of factors associated with low maternal weights, small-for-gestational-age birth, prematurity, low birth weight, and perinatal death was equivalent for maternal weight and body mass index that was less than 10th percentile. This study indicates that in the initial risk assessment of outcomes related to maternal weight, the calculation of maternal body mass index offers no advantage over simply weighing the patient. This finding contrasts with results in nonpregnant women.

Ultrasound measurement of the fetal head: computer versus operator.

In obstetrical ultrasound practice, biparietal diameter, occipito-frontal diameter and head circumference are among the most commonly used fetal measurements. To minimize the limitations associated with manual measurement, we have undertaken an investigation with a focus on (1) the design of a personal computer-based system for automated measurements of biparietal diameter, occipito-frontal diameter and head circumference, and (2) integration of such a system (including measurements of abdomen and femur) into the routine obstetrical ultrasound examination. This report presents preliminary results of a comparison of computer-determined fetal head measurements with those obtained by an operator. Data were obtained from 75 consecutive singleton fetal ultrasound examinations free of any obvious structural anomalies. The computer obtained acceptable measurements of biparietal diameter, occipito-frontal diameter and head circumference from 74 images and failed on one image. There was a highly significant correlation between computer-determined measurements of biparietal diameter (r = 0.986), occipito-frontal diameter (r = 0.958) and head circumference (r = 0.972) and those obtained by the operators. The mean measurement difference (computer minus operator) was 1.87 +/- 1.94 mm for biparietal diameter, 2.82 +/- 4.13 mm for occipito-frontal diameter and -0.36 +/- 9.87 mm for head circumference. These differences were independent of the operator's identity, the instrument used and gestational age. The key finding of this study is that, with the use of inexpensive personal computer technology, it is possible to design and implement a system that can give fetal head measurements which correlate highly with manual determination by a skilled operator and which take a fraction of the time.

Is placenta previa a determinant of preeclampsia?

Low implantation of the placenta has been reported to be associated with a decreased risk for preeclampsia and this has been attributed to increased placental blood flow. However, placenta previa is known to be associated with separation and bleeding, intrauterine growth retardation, and elevated umbilical blood flow resistance by Doppler studies, suggesting decreased umbilical blood flow. To better evaluate the relationship of placenta previa and preeclampsia, 6576 consecutive patients who had ultrasound examination after 28 weeks gestation and delivery at our institution were studied. The placental location, parity, maternal weight, development of preeclampsia, and gestational age were evaluated by using frequency tables and stepwise discriminant analysis. Results showed that placenta previa is not a significant determinant of the development of preeclampsia, but parity, maternal weight, and gestational age contributed significantly to the development of preeclampsia. The finding of decreased incidence of preeclampsia with previa is explained not by increased placental blood flow but by associated maternal characteristics, and particularly by the strong association of previa with premature delivery.

Maternal obesity: a potential source of error in sonographic prenatal diagnosis.

Sonograms from 1622 consecutively scanned singleton pregnancies at a mean gestational age of 28.5 weeks were analyzed to determine whether maternal obesity affected visualization of fetal anatomy. Fetal head (cerebral ventricles), heart (four-chamber view), stomach, kidneys, bladder, diaphragm, intestines, spinal column, extremities, and umbilical cord were classified as visualized or suboptimally visualized. Maternal body mass index was used as a measure of relative leanness. No significant impairment of ultrasound visualization was noted until a body mass index above the 90th percentile, when visualization fell by an average of 14.5%. Reduction in visualization was most marked for the fetal heart, umbilical cord, and spine. Among non-obese women, advancing gestation and decreasing body mass index were the most important determinants of visualization. However, among obese women, body mass index was the best predictor of visualization, with no improvement seen with advancing gestation or duration of examination.