Predictive value, sensitivity, and specificity of ultrasonic targeted imaging for fetal anomalies in gravid women at high risk for birth defects

Ultrasound screening for fetal anomalies in a single center: diagnostic performances twenty years after the Eurofetus Study

PURPOSE

To establish the accuracy of ultrasound in detecting fetal anomalies looking at the concordance between prenatal and postnatal diagnosis.

MATERIALS AND METHODS

Retrospective analysis of concordance between prenatal and postnatal/autoptic diagnosis of fetuses with congenital abnormalities. Data are from a single center (Policlinico di Modena); all fetuses included were born between 2017 and 2018 and with a follow-up of at least 6 months. We included all deliveries (including perinatal deaths) and termination of pregnancy (TOP) for fetal indication. We calculated sensibility, sensitivity, Positive and Negative Likelihood Ratio, positive and negative predictive value of ultrasound.

RESULTS

During the study period 5920 deliveries, including perinatal deaths, and 28 TOP for fetal indication were registered at our center. The prevalence of congenital malformations was 2.6% (153/5920). At least one ultrasound was performed in our center in 1250 women delivering in our unit. All 28 TOP had the anomaly scan performed in our center. Among the total 1278 women scanned in our unit, there were 128 (10%) suspicious scans. In 5/128 (3.9%) cases we diagnosed a false alarm; in 8/128 (6.2%) cases an evolutive malformation with in-utero regression. The prenatal diagnosis was confirmed in 77 (60.2%) cases at birth and in 28/128 (21.9%) at postmortem analysis while there were 10/128 false positive (7.8%). Among the 153 congenital malformations diagnosed at birth, the anomaly scan was performed in our Prenatal Medicine Unit in 92 (60.1%) fetuses. Among these, there were 15 false negatives (9.8%) while in 77/92 (83.7%) the malformation at birth agreed with the sonographic diagnosis. Sensitivity and specificity of ultrasound were 87.5% (IC95 80.2-92.8%) and 99.1% (IC95 98.4-99.6%) respectively with a Positive Likelihood Ratio and Negative Likelihood Ratio of 101.3 (IC95 54.5-188.5) and 0.13 (IC95 0.08-0.2); Positive Predictive Value and Negative Predictive Value were 91.3% (IC95 85-95.1%) and 98.7(IC95 98-99.2%).

CONCLUSION

Anomaly scan in pregnancy allows the diagnosis of congenital malformations with a sensibility of 87.5% and specificity of 99.1%. The main limitations of this study are its retrospective design and that it was conducted in a single referral center.

[Ultrasound screening for birth defects: A medico-economic review]

OBJECTIVES

The systematic use of ultrasound during pregnancy aims at birth defect detection. Our objective was to assess the economic efficiency of prenatal ultrasound screening for fetal malformations.

METHODS

We carried out a literature review on Medline via PubMed between 1985 and 2015, from the economic perspective of the prenatal ultrasound screening for fetal malformations.

RESULTS

The literature on this subject was sparse and we selected only twelve articles presenting relevant economic data, of which only eight were proper medico-economic studies. We found arguments for the economic effectiveness of ultrasound screening for fetal malformation detection, which is largely linked to the terminations of pregnancies and to the cost of the handicaps "avoided". However, none of the reviewed articles could reach medico-economic conclusions. Additionally, we highlighted various elements making economic analyses more complex in this field: the choice of the method, the uncertainty around two essential parameters (the efficiency of ultrasound and the costs of procedures) and the difficulties to compare or to generalize results. We also noticed important methodological heterogeneity among the studies and the absence of French study.

CONCLUSIONS

Previously published data are insufficient to assess the economic efficiency of prenatal ultrasound screening for fetal malformations.

Prenatal sonographic detection of birth defects in 18 hospitals from South America

OBJECTIVE

The purpose of this study was to assess the accuracy of prenatal sonographic diagnosis of birth defects and the gestational age at detection according to the health insurance schemes of mothers in 450 malformed neonates from 18 South American hospitals on the basis of prenatal sonographic records.

METHODS

Between July 2000 and December 2003, 18 hospitals included in the Latin American Collaborative Study of Congenital Malformations (13 from Argentina [8 public and 5 nonpublic], 3 from Brazil [2 public and 1 nonpublic], 1 from Chile [nonpublic], and 1 from Venezuela [public]) voluntarily participated in this prospective observational study, recording fetuses with sonographically detected malformations. Prenatal sonographic descriptions of anomalies were compared with those recorded at birth.

RESULTS

Of 812 anomalies detected at birth, 457 had been prenatally detected (detection rate, 56.3%; 95% confidence interval, 52.8%-59.8%). Before 24 gestational weeks, anencephaly had the highest detection rate. Cleft lip and clubfoot were more easily detected when associated with other anomalies. The detection rates for central nervous system and renourinary malformations were greater than 80%. Detection rates between both health insurance schemes (public and nonpublic) did not show significant differences, but anencephaly, spina bifida, renourinary defects, and cleft lip with or without cleft palate were detected earlier in patients from nonpublic rather than in public hospitals.

CONCLUSIONS

For specific anomalies, South America shows similar levels of prenatal sonographic detection as developed countries. Detection rates during pregnancy were similar for public and nonpublic hospitals, whereas cases were diagnosed earlier in patients from nonpublic hospitals.

Detection of fetal abnormalities by ultrasonography

Diagnostic ultrasonography has achieved an almost universal role in the practice of obstetrics, due to technological improvements in equipment and the experience acquired by well-trained ultrasonographers. Within the general population, over 3% of children reportedly have major congenital malformations that are life-threatening, require major surgery or have serious cosmetic effects. Many of these malformations can be detected antenatally by obstetric ultrasound. The introduction of high frequency transvaginal ultrasonography is a major development in the area of obstetric ultrasonography. Using this method, fetal anomalies have been successfully identified as early as the first trimester of pregnancy, leading some investigators to advocate routine ultrasound examination during pregnancy in order to screen for fetal anomalies at a gestational age that permits consistently accurate diagnosis and maximizes parental choice.

Screening for neural tube defects

The birth prevalence of neural tube defects fell by 95% in England and Wales between 1970 and 1990 largely as a result of antenatal screening, subsequent diagnosis and selective abortion of affected pregnancies. Anencephaly can be diagnosed using ultrasound, whereas both amniotic fluid biochemistry and ultrasound are required for the diagnosis of spina bifida. Both methods have a false-positive rate of about two per 1000 when carried out in high-risk pregnancies. The diagnostic results are likely to be better if the two methods are used in parallel. Maternal serum alpha-fetoprotein screening at 16-18 weeks gestation can detect about 75% of pregnancies affected by spina bifida. Routine ultrasound anomaly screening, usually performed at 18-20 weeks gestation, can detect a similar proportion. New developments indicate that earlier, more accurate detection may be possible but more research will be needed before this can be established.

Le contrôle de qualité en échographie prénatale : intérêt de la biométrie

Because of an increasing demand for limited health care resources as well as an increasing impact of legal aspects in ultrasound practice, it has become necessary to ensure that screening procedures are cost-effective and clinically effective and to develop systems that could help sonographists in certifying their practice. Based on the literature, various approaches for quality control are reviewed. Special emphasis is put on the use of fetal biometry and statistical tools to develop quality control systems based on both qualitative and quantitative approach. Besides their potentials for audit and quality control, such tools could also be useful during the process of training.

An abnormal screening ultrasound: concordance with a tertiary obstetrical ultrasound unit

OBJECTIVE

To determine concordance of ultrasound diagnosis in referrals to a tertiary obstetrical ultrasound unit (TOU) for suspected abnormalities.

STUDY DESIGN

Consecutive referrals for "abnormal outside ultrasound" during a 6-month period were compared with the TOU ultrasound diagnosis. Concordance of diagnosis was compared on the basis of organ system involved and referral for single or multiple suspected abnormalities. Chi(2) analysis was used; p < 0.05 was considered significant.

RESULTS

Of 104 consecutive referrals reviewed, 42 (40.4%) had no abnormality documented at the TOU. Of the 62 abnormal ultrasound scans at the TOU, 78.3% were concordant. Concordance based on organ system involvement was central nervous system, 30.3%; cardiothoracic, 66.7%; gastrointestinal, 63.6%; genitourinary, 50%. Referrals for a single suspected anomaly were statistically no more likely to have a normal TOU ultrasound scan (40.4%) than those referred for multiple suspected anomalies (36.4%, p > 0.05).

CONCLUSIONS

Most referrals to a tertiary center for "abnormal outside ultrasound" will be diagnosed with an abnormality.

Ultrasound in prenatal diagnosis: polemics around routine ultrasound screening for second trimester fetal malformations

Ultrasound for routine fetal malformation screening has been polemical from its early beginning because of the very broad range of diagnosis rates disclosed, i.e. from 13% to 82%, average 27.5%. A review of available studies is proposed to assess objectively the efficacy of ultrasound, considering also economical, ethical and methodological aspects as influential factors for choosing a routine screening policy. The utility of fetal malformation diagnosis before birth is brought forward, including second opinion, karyotyping, poly-disciplinary case discussion prior to management. Method and material of reviewed studies considerably vary and might influence the sensitivity results, as the choice of the population sample and selection of pregnant women, gestation age at screening, distribution of malformation among systems or tracts, exclusion of some fetal malformation and the routine practice of autopsy. Efficiency of screening studies is compared, and among them Radius and Eurofetus studies. Average sensitivity is finally considered as satisfactory in the daily practice when operated by trained personnel. The importance of additional factors for successful screening are emphasized such as education, equipment quality and fetal ultrasound examination at different gestation age for a better understanding of natural history of fetal morphology.

The practical importance of pedigree analysis in women considering invasive prenatal diagnosis for advanced maternal age or abnormal serum screening tests

Genetic counselling prior to prenatal diagnosis subserves several functions, one of them to put the planned prenatal test into the wider context of the personal and familial medical history. Even though considered a pivotal part of counselling, little is known about the informational yield and practical relevance of a comprehensive pre-test pedigree analysis. This is particularly true for patients who do not consider prenatal diagnosis for a specific heritable disorder with a high recurrence risk in the ongoing pregnancy, but for a moderate risk for conditions such as Down syndrome that mostly arise de novo. We analysed the informational yield of pedigree analysis for such patients through a retrospective analysis of 1356 consecutive genetic counselling sessions. All cases were referred for advanced maternal age or an abnormal result upon triple serum marker screening. 148 cases (10.9%) were classified as having a significant and previously unknown genetic or teratologic risk factor for the fetus that was uncovered through pedigree analysis. Of these cases, 55% could be recommended a specific prenatal test covering the previously unknown genetic risk factor.

Fetuses and infants with congenital urinary system anomalies: correlation between prenatal ultrasound and postmortem findings

OBJECTIVE

Detection of congenital urinary system anomalies is an important part of the prenatal ultrasound examination. The present study compares prenatal ultrasonographic findings and postmortem examinations of fetuses and infants with renal and urinary tract anomalies.

DESIGN

Criteria for inclusion were an ultrasound examination at the National Center for Fetal Medicine (Trondheim, Norway) and autopsy performed during the period 1985-94. Results from the ultrasound examination and autopsy regarding urinary system anomalies were categorized according to the degree of concordance.

RESULTS

Urinary system anomalies were found in 112 (27%) of 408 fetuses with congenital anomalies. The renal and/or urinary tract anomaly was the principal reason for induced abortion or cause of death in 50 cases (45%). In 97 (87%) of the 112 cases there was full agreement between the ultrasound observations and the autopsy findings. In five cases the autopsy revealed minor findings not mentioned in the ultrasound report. The main diagnosis was thus correct in 102 cases (91%). In four cases major autopsy findings had not been found by ultrasound examination; in another four, none of the autopsy findings were suspected by ultrasound, and in two, minor ultrasound findings were not confirmed at autopsy.

CONCLUSIONS

The accordance between ultrasound diagnoses and postmortem examinations proved to be satisfactory. The close co-operation between ultrasonographers and perinatal pathologists is mutually beneficial. In addition to complementing prenatal diagnosis, postmortem examination is of vital importance for the quality control of ultrasonography in fetal diagnosis and plays an important role in genetic counseling.

The performance of routine ultrasonographic screening of pregnancies in the Eurofetus Study

OBJECTIVES

The purpose of the Eurofetus Study was to evaluate the accuracy of the antenatal detection of malformations by routine ultrasonographic examination in unselected populations.

STUDY DESIGN

All ultrasonographic diagnoses of malformations and the outcomes of the fetuses were prospectively recorded in 61 European obstetric units over a 3-year period (1990-1993). Also recorded were all cases of malformation diagnosed after abortion or birth for the mothers who underwent follow-up in these centers.

RESULTS

Of 3685 malformed fetuses, 2262 had received diagnoses during pregnancy (sensitivity, 61.4%). Of a total number of 4615 malformations, 2593 were detected (sensitivity, 56.2%). The detection sensitivity was higher for the major than for the minor abnormalities (73.7% vs 45.7%), and the diagnosis was made earlier in the pregnancy (24.2 weeks vs 27.6, P <. 01). Overall, 55% of the major abnormalities were detected within 24 gestational weeks. Within each severity group the accuracy of detection depended on the system. For the major abnormalities it was better for the central nervous system (88.3%) and urinary tract (84. 8%) but lower for the heart and great vessels (38.8%). Detection of minor abnormalities was also effective for the urinary tract (89.1%) but not for the heart and great vessels (20.8%) or the musculoskeletal system (18%). Detection of abnormalities had an influence on the rate of termination of pregnancy. The rate of live births for the mothers bearing fetuses with major abnormalities was lower than that for the mothers in whom no abnormalities were detected, mainly because of the higher rate of elective terminations of pregnancy in the former group.

CONCLUSION

Systematic ultrasonographic screening during pregnancy can now detect a large proportion of fetal malformations, although some still escape detection.

Routine obstetrical ultrasound at 18-22 weeks: our experience on 7,236 fetuses

OBJECTIVE

This study aimed at examining the detection rate of congenital abnormalities by using routine ultrasonography at 18-22 weeks of gestation.

METHODS

The sample included 7,236 fetuses. A detailed sonographic examination was performed in each fetus and a neonatal evaluation or pathology examination was made to confirm the prenatal findings.

RESULTS

The total prevalence of fetal abnormalities in our sample was 2.24% (162/7,236). There were 29/162 (17.9%) fetuses with CNS abnormalities, 27/162 (16.7%) fetuses with gastrointestinal abnormalities, and 28/162 (17.3%) fetuses with urinary tract abnormalities. There were also 31/162 (19.1%) fetuses with cardiovascular abnormalities, 26/162 (16.0%) with malformation of the limbs and musculoskeletal system, and 21/162 (13%) fetuses with other various abnormalities. The overall sensitivity in detecting fetuses with congenital abnormalities was 80.25% (130/162). The sensitivity per system was 93.1% (27/29) for CNS, 45.2% (14/31) for cardiovascular system, 85.2% (23/27) for gastrointestinal system, 85.7% (24/28) for urinary system, 84.6% (22/26) for musculoskeletal system, and 95.2% (20/21) for the rest of the abnormalities detected. We performed 40 pregnancy terminations in the group of malformed fetuses. Among the fetuses considered as normal, 1.7% had chromosomal abnormalities.

CONCLUSIONS

The results indicate that routine sonographic examination at 18-22 weeks of gestation can detect the majority of congenital abnormalities. More experience is needed for the examination of the cardiovascular system, where the sensitivity was particularly low (14/31 or 45.2%).

Correlation of prenatal ultrasound diagnosis and pathologic findings in fetal anomalies

This retrospective study compared the prenatal ultrasound (US) diagnosis with autopsy findings in 61 intact fetuses following induced abortion and 36 fragmented fetuses from dilatation and evacuation (D&E). In intact fetuses, complete agreement between US diagnosis and autopsy findings was achieved in 65.6% of cases in the central nervous system (CNS) and 47.5% in other somatic organ systems (SOS). There were major differences between US and autopsy findings involving the CNS in 6.5% of cases and SOS in 27.9%. Correlation was better for evaluation of renal anomalies (complete agreement in 63.6% of 11 suspected cases, 2 false-positive and no false-negative cases) than congenital heart disease (complete agreement in 27.3% of 11 suspected cases, 5 false-positive and 3 false-negative cases). In D&E specimens, a prenatal diagnosis of neural tube defect (NTD) was confirmed in 90% of cases. However, due to fragmentation of fetal parts, the US diagnosis in the CNS could not be confirmed totally (69.4%) or partially (2.8%) in fetuses with chromosomal abnormalities (ChA) or multiple congenital anomalies (MCA). Nonetheless, the US diagnosis of SOS was confirmed in six cases on D&E, including Meckel-Gruber syndrome, cystic hygroma, renal agenesis with contralateral renal dysplasia, cardiac defect, fetal hydrops, and tracheal atresia. Our results show that a thorough autopsy of an intact fetus after abortion is necessary to confirm prenatal diagnosis and allow proper management and counseling. The pathologic examination of D&E specimens can reliably confirm the US diagnosis of NTD, but it is very limited in identifying other fetal anomalies.

Ultrasonographic assessment of abnormal pregnancy

Ultrasonographic imaging is widely used in small animal practice for the diagnosis of pregnancy and the determination of fetal number. Ultrasonography can also be used to monitor abnormal pregnancies, for example, conceptuses that are poorly developed for their gestational age (and therefore are likely to fail), and pregnancies in which there is embryonic resorption or fetal abortion. An ultrasound examination may reveal fetal abnormalities and therefore alter the management of the pregnant bitch or queen prior to parturition. There are, however, a number of ultrasonographic features of normal pregnancies that may mimic disease, and these must be recognized.

Sensitivity of routine ultrasound screening of pregnancies in the Eurofetus database. The Eurofetus Team

In this prospective study, we recorded details on 3,685 fetuses with congenital structural abnormalities from an unselected population of women who underwent routine ultrasound examinations during their pregnancies. Overall, 2,262 fetuses were diagnosed as being abnormal before birth (sensitivity = 61.4%). The total number of abnormalities was 4,615, of which 1,733 (37.5%) were major abnormalities. The overall number of detected abnormalities was 2,593 (sensitivity = 56.2%). If only major abnormalities were considered, the sensitivity rose to 73.7%, compared to only 45.7% for the minor abnormalities. Within each severity group, the accuracy of detection varied across systems. For the major abnormalities, it was higher for the central nervous system (88.3%) and urinary tract (84.8%), but lower for heart and great vessels (38.8%). Detection of minor abnormalities was also effective for the urinary tract (89.1%), but not for the heart and great vessels (20.8%) and the musculoskeletal system (18%).

Routine ultrasound screening of congenital anomalies. An overview of the European experience

Results from ultrasound in low-risk pregnant women are significant when routine screening is performed on a large population because the anomalies are rare. Professionals expect from routine ultrasound objective information that cannot usually be obtained by clinical procedures. Parents seek reassurance about the absence of fetal congenital anomalies and overall fetal health. Therefore, Europeans view routine ultrasound as a part of obstetrical care, capable of filling important gaps by delivering much key information for improving obstetrical practice. Fetal anomalies screening (FAS) requires higher education and qualifications than obstetrical ultrasound. The health insurance systems support ultrasound screening and allow its spread in most European countries; approximately 98% of pregnant women are examined by ultrasound and, frequently, two to three times (usually once per trimester). Detection rate of congenital anomalies is about 28% in geographical areas (private practice and hospitals), 60 to 80% in Ob/Gyn's ultrasound labs. Routine ultrasound screening policy has not proved to result in an immoderate use of ultrasound; on the contrary, chaotic use of routine ultrasound can lead to an unproductive and excessive number of scans. New trends in FAS, such as the early detection of fetal defects and chromosomal anomalies, bring more arguments for routine screening. Effectiveness should increase by enhancing education and training and the systematic referral for FAS to accredited laboratories.

The routine or screening obstetrical ultrasound examination

The debate concerning the value of routine screening ultrasound in the low-risk patient continues. The most likely benefits are obstetrical, with confirmation of dates, detection of multiple gestation, baseline growth data, and location of the placenta being primary advantages gained from such an examination. The detection of the unexpected major fetal malformation has always been the least likely benefit of routine ultrasound. Furthermore, the majority of reports have been retrospective, uncontrolled, and too small to resolve the question. The RADIUS study was intended to solve these problems, but suffered from such intense selection that the final population for study had little need for medical care at all and little relevance to the average population. The rate of adverse outcomes among the control group was so low that few interventions would appear useful. Furthermore, the analysis of the RADIUS data appeared to suggest bias by underestimating the diagnostic sensitivity of ultrasound for major anomalies, and de-emphasizing those statistically significant obstetrical benefits that were recorded. An attempt at cost-benefit analysis by the RADIUS study misrepresented the cost of routine ultrasound by overestimating the size of the low-risk population, arbitrarily costing out two scans instead of one, and therefore overestimated the cost savings of omitting these examinations. Diagnostic sensitivity of the screening obstetrical ultrasound examination appears to be highest in high-risk patients examined by highly specialized ad experienced personnel that may be of limited availability. diagnostic sensitivity may be quite good, however, even in low-risk patients with a basic or routine examination if recognized guidelines for content are followed and referral to experienced referral resources for unclear or suspicious images is liberally practiced. Optimal service and minimum liability exposure will result if the following guidelines are followed: 1. The obstetric population should be carefully screened for historical or clinical risk factors that might indicate increased probability of fetal abnormality. Identification of such increased risk should cause consideration of referral. 2. The screening ultrasound examination should be methodical and complete and include examination of each of several recommended scanplane views to maximize diagnostic sensitivity. 3. The performance of a complete and methodical examination should be carefully documented with both descriptive text and image records to show that a standard of care service was provided. 4. Referral for second opinion should be easily considered and easily obtained in the case of any suspicious finding. Should every obstetrical patient have an ultrasound examination? Only if it is competently performed, properly recorded, and if the patient is aware of appropriate goals and limitations. The ideal gestational age is between 18 and 22 completed weeks.

Antenatal depiction of fetal digits with three-dimensional ultrasonography

OBJECTIVE

The effectiveness of three-dimensional ultrasonography in visualizing fetal digits was examined.

STUDY DESIGN

The digits of 72 fetuses, including 2 with skeletal dysplasia, were examined prospectively with both conventional and three-dimensional ultrasonography.

RESULTS

Complete visualization of all fetal digits was obtained more often with three-dimensional ultrasonography than with two-dimensional ultrasonography.

CONCLUSION

Three-dimensional ultrasonography has the potential to facilitate depiction of fetal digits, which may enhance prenatal identification of fetal malformations and chromosomal abnormalities in high-risk pregnancies.

Second trimester routine ultrasound and abnormal findings

OBJECTIVE

To estimate the detection rate of abnormal findings, especially fetal anomalies, at second trimester ultrasound screening performed in a way representative of Swedish antenatal clinics.

DESIGN

A prospective study carried out over two years in Uppsala county, Sweden, including 8,228 unselected pregnant women (8,345 fetuses). The ultrasound scans were performed by specially trained midwives.

MAIN OUTCOME MEASURES

The number of abnormalities suspected by the midwives and the number of abnormalities confirmed by the obstetricians were registered, as was pregnancy outcome for these cases.

RESULTS

Midwives reported suspected abnormalities at the screening procedure in 59 cases (0.7%), abnormalities were confirmed by obstetricians in 42 cases (0.5%, of which 0.36% were fetal malformations). Seventeen of these 42 pregnancies were terminated and 11 ended with miscarriages or intrauterine fetal deaths. Fourteen of the 42 pregnancies ended with a live born infant, of which two died postnatally.

CONCLUSIONS

The described ultrasound screening procedure led to suspected abnormalities in 0.7% of the scanned cases and to confirmed abnormalities in 0.5% of the cases. The outcome for the confirmed abnormalities was poor, as 71% were either terminated or ended with miscarriage or perinatal death.

Antenatal sonographic diagnosis of clubfoot: a six-year experience

In the period 1988 through 1993, 6351 pregnant women were referred to the Department of Obstetrics and Gynaecology, University "La Sapienza", Roma, for suspected fetal anomalies or maternofetal problems. All underwent serial transabdominal and/or transvaginal ultrasound scanning, which revealed a total of 235 fetuses with hydrocephalus, cardiac, or musculoskeletal malformations. Forty-one clubfeet were detected in 27 pregnancies in the early part of the second trimester of pregnancy. Of these, 14 feet in eight patients were isolated, and were classified as idiopathic. A clubfoot was associated with neural tube defects in six patients, with anomalies of the urinary and/or digestive system in a further six, with a cystic hygroma in two, and with other musculoskeletal abnormalities in the other six patients. Amniocentesis revealed an abnormal karyotype in six fetuses (22.2%). In only two cases was oligohydramnios present. In both these patients, a fetal urinary tract malformation was present Polyhydramnios was found in 18 cases, and a normal amount of amniotic fluid was found in the remaining seven cases. Polyhydramnios was present in six of the eight idiopathic clubfoot fetuses. Clubfoot is associated with musculoskeletal and visceral anomalies in a high proportion of cases. The association of clubfoot with polyhydramnios in a high proportion of cases does not support the hypothesis of intrauterine moulding as an etiological factor in its development. Ultrasonographical prenatal detection of a clubfoot should prompt amniocentesis, as the condition is associated with an abnormal karyotype in a significant proportion of cases.

Ultrasonography in pregnancy and fetal abnormalities: screening or diagnostic test? IPIMC 1986-1990 register data. Indagine Policentrica Italiana sulle Malformazioni Congenite

The aim of the present study was to assess the sensitivity of ultrasound diagnosis used as a screening test in detecting major congenital anomalies in the prenatal period in a large nation-based multicentre setting. Data from the IPIMC register were collected in the period 1986-1990. One hundred and thirty-five hospitals, located in 17 out of the 20 regions in Italy, participated in the register. Study cases were 3479 infants with major congenital anomalies diagnosed at birth or in the first week of life. Subjects with chromosomal anomalies or multiple defects were excluded. The sensitivity of ultrasound prenatal diagnosis was 49.5 per cent for central nervous system anomalies, 3.8 per cent for congenital heart diseases, 17.1 per cent for gastrointestinal tract defects, 46.6 per cent for abdominal wall defects, 74.8 per cent for urinary tract anomalies, and 22.9 per cent for skeletal abnormalities. The detection rate for diaphragmatic hernia was 24.2 per cent. Overall, only 18 per cent of the defects diagnosed in utero were detected before 24 weeks' gestation. The sensitivity of prenatal diagnosis was 30.1 and 19.0 per cent in the northern, central, and southern regions, respectively. In light of its low sensitivity, ultrasonography as a screening test in the general population should be abandoned, although some improvement in its performance should be expected following adequate training of the ultrasound staff and the use of good technical equipment.

Impact of prenatal screening and diagnosis on the epidemiology of structural congenital anomalies

OBJECTIVE

To assess the impact of prenatal screening on the birth prevalence of three categories of structural congenital anomaly: abdominal wall defects (omphalocele and gastroschisis), renal agenesis/dysgenesis, and limb reduction defects.

SETTING

Glasgow, Scotland, United Kingdom.

METHODS

Data on the selected defects were obtained retrospectively from the population based Glasgow Register of Congenital Anomalies for the period 1980-91 inclusive. The register records all clinical or laboratory diagnoses of congenital anomaly in live births, stillbirths, and induced abortions occurring in women resident within the boundaries of the Greater Glasgow Health Board. The secular trends in the proportions of the defects diagnosed prenatally and terminated after screening, and in their prevalence at birth and during pregnancy, were examined. A total of 154,845 births were surveyed: 309 cases were identified in the selected anomaly categories.

RESULTS

83 cases of omphalocele/gastroschisis (5.4/10,000 births), 92 cases of renal agenesis/dysgenesis (5.9/10,000 births), and 134 cases of limb reduction defects (8.7/10,000 births) were found. Marked increases occurred over the study period in the proportions of cases diagnosed prenatally but not in the proportions terminated. The greatest difference between the prevalence at birth and during pregnancy was found for omphalocele. There were no significant secular trends in the prevalence of the selected defects.

CONCLUSIONS

Prenatal screening has made a limited epidemiological impact on the prevalence of these defects. It has been moderately (but inconsistently) effective in the avoidance of births of infants with omphalocele/gastroschisis and renal agenesis/dysgenesis but not of limb reduction defects. Future efforts should be directed towards improving the technical aspects of the ultrasonographic detection of fetal abnormalities and exploring in detail, locally, the reasons for the varying pattern of decision making about termination of pregnancy among prospective parents.

Prenatal detection of internal urinary system's anomalies. A registry-based study

Prenatal diagnosis performed by ultrasound scan is now a routine part of antenatal care in our region. How many fetal anomalies are actually detected by this procedure? We have used our registry of congenital malformations to answer this question regarding to Internal Urinary System (IUS) anomalies. The mean time of detection of IUS anomalies was 29 weeks of pregnancy (12-39). The sensitivity of prenatal diagnosis of IUS anomalies by ultrasonographic examination was 59.3% for isolated malformations (fetuses with only one anomaly) and 46.0% for multiple malformed children with IUS anomalies. For all cases of IUS anomalies the percentage of prenatal detection was 56.0. Termination of pregnancy was performed in 9.4% of the cases.

Transvaginal ultrasonography at early pregnancy cannot be used alone for targeted organ ultrasonographic examination in a high-risk population

OBJECTIVE

A study was performed to evaluate whether early second-trimester (13 to 16 weeks) transvaginal scan can be used alone for structure evaluation of the fetus or whether it should be followed by a transabdominal scan performed at 18 to 20 weeks of gestation.

STUDY DESIGN

A total of 536 pregnant women at high risk for birth defects were examined by transvaginal ultrasonography at 13 to 16 weeks' gestation. This was followed by a transabdominal scan at 18 to 20 weeks of pregnancy. Aborted specimens were examined by a pediatric pathologist in terminated pregnancies, and newborn babies were examined by a pediatrician to detect congenital anomalies.

RESULTS

Transvaginal ultrasonography performed at 13 to 16 weeks' gestation identified 42 structural anomalies. Of these, 24 pregnancies were terminated and one fetus died. The other 17 fetuses and the rest of the population underwent a second transabdominal survey at 18 to 20 weeks' gestation, which identified eight structural anomalies that were not diagnosed by the previous examination. In five cases the diagnosed anomaly disappeared. Together, the scans brought about the detection of 41 of 46 abnormal fetuses (89%).

CONCLUSIONS

Because a significant number of birth defects (17.4%) was not detected by early second-trimester vaginal scan, we recommend that whenever early transvaginal ultrasonographic examination is performed it should be followed by a transabdominal scan at the most advanced stage of pregnancy at which an abortion is still feasible.

The accuracy of prenatal ultrasonography in detecting congenital anomalies

OBJECTIVES

The purpose of this study was to evaluate the accuracy of prenatal ultrasonography in detecting congenital anomalies.

STUDY DESIGN

We studied all singleton births or fetal deaths with one or more congenital defects delivered during the study period who had had one or more ultrasonographic examinations performed at or after 16 weeks' gestation and a random sample of defect-free newborns similarly examined by ultrasonography. Congenital anomalies reported on either the infants' postdelivery medical record or the fetal autopsy report were our standard. Prenatal ultrasonographic findings reported during gestation and therefore "blind" to the postdelivery outcome were then compared with the standard.

RESULTS

The overall sensitivity of ultrasonography in detecting defects was 53%. The overall specificity was 99%. Ultrasonography proved to be highly sensitive (89%) for prevalent lethal malformations. However, serious cardiac defects, microcephalus, and many musculoskeletal deformities were missed by ultrasonography.

CONCLUSION

Ultrasonography is sensitive in detecting many lethal malformations. However, a negative prenatal ultrasonographic examination does not provide absolute assurance that a fetus is defect free.

Evaluation of prenatal diagnosis of limb reduction defects by a registry of congenital anomalies

Prenatal diagnosis performed by ultrasound scan is now a routine part of antenatal care in our region. How many fetal anomalies are actually detected by this procedure? We have used our registry of congenital malformations to answer this question regarding limb reduction defects (LRDs). The mean time of detection of LRDs was 26 weeks of pregnancy (range 16-32 weeks). The sensitivity of prenatal diagnosis of LRDs by ultrasonographic examination was much lower for isolated malformations (fetuses with only one anomaly) than for multiply malformed children with LRDs, 4.0 and 18.2 per cent, respectively. For all cases of LRDs, the percentage of prenatal detection was 11.5. Termination of pregnancy was performed in 6.7 per cent of the cases.

Anencephaly: changes in prenatal detection and birth status, 1972 through 1990

OBJECTIVE

We assessed at a large university hospital the effect of prenatal diagnosis on the birth of infants with anencephaly between 1972 and 1990.

STUDY DESIGN

All 175 affected infants were identified by a postnatal Malformations Surveillance Program, which included stillborn infants and elective terminations in the second trimester. The affected infants were subdivided into those whose mothers had always planned delivery at this hospital (nontransfers) and those whose mothers had planned delivery elsewhere but were transferred after the prenatal detection of the fetal abnormality (transfers).

RESULTS

In the 1970s half the infants were anencephaly were born alive; the average gestational age was 35.6 weeks, and only a few were diagnosed prenatally. By 1988 to 1990 all affected infants were diagnosed either by prenatal ultrasonography or as the result of maternal serum alpha-fetoprotein screening; the parents elected to terminate the pregnancies, and the average gestational age was 19.6 weeks.

CONCLUSION

Prenatal detection and the selection by parents of the option of elective termination of pregnancy has altered significantly the birth status of infants with anencephaly since 1972.

Doppler umbilical velocimetry in women with polydrug abuse including cocaine

Doppler umbilical artery velocimetry was performed in 40 chemically dependent women. The mean S/D ratio was 2.7 with 15/66 values greater than or equal to 3.0. No cases of absent or reverse end-diastolic flow were noted. The mean S/D ratio in women with positive toxicologies for cocaine use was not statistically elevated compared to women with negative screens (2.8 versus 2.7, P = 0.51). In this study an S/D ratio greater than or equal to 3.0 had a sensitivity of 40% for identifying intrauterine growth retardation with a positive predictive value of 20%.

Screening and detection of congenital malformation

Congenital malformations often occur sporadically and unpredictably, and a method of population screening to identify at-risk pregnancies would be of great value. Routine ultrasonography has some appeal in this regard. Unfortunately, the literature indicates a relatively poor sensitivity, with usually 30% or less of malformations identified or suspected by this means. Substantially better results have been described with ultrasonography targeted on the basis of screening ultrasonography or clinical findings, but these studies involve highly selected subjects examined carefully by experienced ultrasonographers, and their results are not relevant to population screening. A questionnaire survey of experts in the field indicated disagreement with the separation of screening and targeted ultrasonography, widely varying estimates of the accuracy of either, and average changes of $209 and $263, respectively. Theoretical considerations of the various types of malformations, their frequencies, and the likelihood of ultrasonographic detection reveal a minority of defects in which ultrasonography is both accurate and useful clinically. Ultrasonography seems to be of little potential as a means of screening for congenital malformation because of relatively low sensitivity and uncertain cost effectiveness.

Tables for estimation of individual risks of fetal neural tube and ventral wall defects, incorporating prior probability, maternal serum alpha-fetoprotein levels, and ultrasonographic examination results

Tables are provided for estimation of the risk of open spina bifida in patients who have elevated maternal serum alpha-fetoprotein levels but normal results on detailed anatomy ultrasonographic scan. Risks are provided for various prior population risks, for various levels of elevated maternal serum alpha-fetoprotein, and for various assumptions about the sensitivity of ultrasonographic examination. The formula used is based on sequential multiplication of odds with the use of Bayes' theorem, but an arbitrary reduction (to the power of 0.5) in the degree to which ultrasonographic information modifies the odds has been made to allow for the nonindependence of ultrasonography and maternal serum alpha-fetoprotein tests. The wide range of resulting risks shows that the decision to offer amniocentesis after a negative scan should be individualized.

Prenatal informed consent for sonogram: an indication for obstetric ultrasonography

Currently in the United States there is widespread agreement that obstetric ultrasonography should be performed when indicated, based on a beneficence-based calculus. However, there is considerable uncertainty that routine ultrasonography is similarly indicated for every pregnant woman. We argue that the standard of care demands that prenatal informed consent for sonogram be accepted as an indication for the prudent use of obstetric ultrasonography performed by qualified personnel. Prenatal informed consent for sonogram, a primarily autonomy-based indication, should be given the same weight in clinical judgment and practice as the beneficence-based indications listed by the National Institutes of Health consensus panel.

Evaluation of routine ultrasound examination for the prenatal diagnosis of malformation

In 1986, a retrospective survey was undertaken in the southern part of the province of Hainaut, Belgium, in order to measure the frequency of ultrasound examinations during pregnancy and to evaluate the effectiveness of the routine practice of echography screening for the detection of congenital malformations in an unselected population. The reference populations comprised 8316 pregnancies covered by the EUROCAT Registry of Hainaut. In 1986, 190 congenital malformations cases were registered. For each of the 190 cases, one control ending in the birth of a non-malformed infant was retrospectively selected. The analysis showed that an average of four ultrasound examinations were performed during pregnancy. When all malformations are considered, the sensitivity of the screening is 14% (27/190). Sensitivity of detection varied from 100% for gross malformations such as anencephaly to 0% for defects of a minor size such as facial clefts. In these 27 cases, obstetrical interventions following prenatal diagnosis were termination of pregnancy in 14 cases and induction of labor in 3 cases. Antenatal care was planned in 8 cases, 5 of which had early surgical repair. In the control group, a malformation was suspected in 3 of the 144 pregnancies (specificity of detection, 98%).

Antenatal ultrasound for fetal anomalies: importance of perinatal autopsy

Sixty-one instances of congenital anomalies identified prenatally by ultrasound were reviewed to determine whether autopsy provided important additional information. An important finding was defined as one which would affect: 1) genetic counseling; 2) diagnosis of a syndrome; 3) determination of etiology or pathogenetic mechanism of the anomaly; or 4) interpretation of severity of the anomalies. In 28 cases (46%), post-mortem examination provided such information. All of these infants had multiple anomalies; correlations with oligohydramnios and poor fetal outcome were noted. Autopsy provided no additional meaningful information in 30 cases (49%), the majority (77%) of whom had isolated anomalies. In 3 cases (5%), due to tissue autolysis, autopsy provided less information than the previous ultrasound. Although most fetal anomalies are readily diagnosed by ultrasound, we found that post-mortem examination is still necessary: 1) to confirm a prenatal diagnosis; 2) to delineate multiple anomalies; 3) when the ultrasound examination is limited by oligohydramnios; and 4) to obtain tissue for microscopic examination, cytogenetic and biochemical analysis, if these studies have not been performed prenatally.

Should maternal alpha-fetoprotein estimation be carried out in centers where ultrasound screening is routine? A sensitivity analysis approach

We describe a case of small, open spina bifida that was detected on the basis of maternal serum alpha-fetoprotein levels but consistently missed on careful ultrasound examination. This prompted us to reexamine the policy (adopted by an increasing number of departments) of relying exclusively on ultrasound examination for the detection of spinal lesions. In this article we therefore analyze the number of additional cases of spina bifida that could be detected by offering maternal serum alpha-fetoprotein screening in addition to a routine ultrasound examination. Our calculations are made on the basis of published assessments of the performance of these tests and on the assumptions about test independence. We test our conclusions against a wide variety of test performance values in a detailed sensitivity analysis. The final decision to carry out maternal serum alpha-fetoprotein testing is a value judgment, but this decision should be based on realistic numeric estimates of the potential benefits and hazards of this procedure.

Caution in antenatal intervention

We assessed 18 fetuses who harbored a urinary tract malformation that was diagnosed by antenatal sonography. The antenatal diagnosis corresponded to the postnatal diagnosis in 66 per cent of the cases. We review the course of 6 fetuses who had catheters placed percutaneously to drain dilated urinary tracts that were believed to be caused by posterior urethral valves (5) or an obstructed megaureter (1). Only 2 of these fetuses exhibited valves postnatally. No fetus had any recognized benefit from the antenatal intervention. We found that sonography may not readily differentiate fetuses with hydronephrosis with obstruction from those without obstruction. From this experience we conclude that intervention in pregnancies suspected of harboring a fetus with a malformed urinary tract should be done cautiously. Antenatal sonography is useful to identify the fetus with a dilated urinary tract. This identification permits perinatal specialists to be alerted so that preparations for reconstructive surgery in such cases can be made early postpartum.