Frequency and prediction of persistent urinary tract dilation in third trimester and postnatal urinary tract dilation in infants following diagnosis in second trimester.

OBJECTIVE: To determine the frequency, associated characteristics and prognostic value of the current risk stratification system for prenatal urinary tract dilation (UTD) for predicting persistent UTD in the third trimester and subsequent postnatal UTD in the infant, following diagnosis in the second trimester. METHODS: This was a single-institution retrospective cohort study of singleton pregnancies diagnosed with unilateral or bilateral UTD in the second trimester (before 28 weeks' gestation) with follow-up in the third trimester (at or after 28 weeks) between January 2017 and May 2019. In all cases, the prenatal diagnosis and stratification to low-risk (Grade A1) or increased-risk (Grade A2-3) UTD was made using the 2014 UTD consensus classification system. The primary outcomes included persistent prenatal UTD in the third trimester and postnatal UTD up to 6 months of age. We performed multivariable analysis to assess whether patient and second- and third-trimester sonographic characteristics (such as UTD laterality, other renal abnormality (calyceal dilation, abnormal parenchymal appearance, abnormal ureter or bladder) and anteroposterior renal pelvic diameter (AP-RPD)) were associated with the study outcomes. We assessed the predictive value of the current risk stratification system (Grade A1 vs Grade A2-3) in the second and third trimesters for persistent prenatal UTD and postnatal UTD using the area under the receiver-operating-characteristics curve (AUC). RESULTS: Of 26 620 second-trimester ultrasound assessments in the study period, 347 patients were diagnosed with UTD in the second trimester and had third-trimester follow-up, of whom 150/347 (43% (95% CI, 38-49%)) had persistent UTD in the third trimester. Among the 282/347 (81%) patients with postnatal follow-up available, the frequency of postnatal UTD was 49/282 (17% (95% CI, 13-22%)), and among the subset with persistent UTD in the third trimester, the frequency of postnatal UTD was 46/102 (45% (95% CI, 35-55%)). The most frequent postnatal diagnosis was transient UTD (76%), followed by duplicated collecting system (10%). Of infants originally diagnosed with UTD in the second trimester, 2% (7/347) required surgery; stated differently, of the 49 infants with postnatal UTD, 14% (7/49) required surgery. At second-trimester diagnosis, sonographic predictors of both persistent prenatal UTD and postnatal UTD included the presence of other renal abnormality and UTD Grade A2-3. At third-trimester follow-up, predictors of postnatal UTD were larger mean AP-RPD and UTD Grade A2-3, while all cases had other renal abnormality. Second-trimester diagnosis of UTD Grade A2-3 had satisfactory discrimination for predicting persistent prenatal UTD (AUC, 0.64 (95% CI, 0.58-0.70)) and postnatal UTD (AUC, 0.72 (95% CI, 0.63-0.81)), as did third-trimester UTD Grade A2-3 for predicting postnatal UTD (AUC, 0.66 (95% CI, 0.56-0.76)). CONCLUSIONS: The majority of cases of prenatal UTD did not result in postnatal UTD, and of those that did, very few required surgery. Follow-up third-trimester assessment after a second-trimester diagnosis of UTD is warranted. The current risk stratification system by UTD grade, based on the 2014 UTD consensus classification, can be used to predict postnatal UTD with fair accuracy. Further research is needed to determine whether the predictive performance of this system can be improved by incorporating additional risk factors. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

United States' experience in nuchal translucency measurement: variation according to provider characteristics in over five million ultrasound examinations.

OBJECTIVE: The Nuchal Translucency Quality Review (NTQR) program has provided standardized education, credentialing and epidemiological monitoring of nuchal translucency (NT) measurements since 2005. Our aim was to review the effect on NT measurement of provider characteristics since the program's inception. METHODS: We evaluated the distribution of NT measurements performed between January 2005 and December 2019, for each of the three primary performance indicators of NT measurement (NT median multiples of the median (MoM), SD of log10 NT MoM and slope of NT with respect to crown-rump length (CRL)) for all providers within the NTQR program with more than 30 paired NT/CRL results. Provider characteristics explored as potential sources of variability included: number of NT ultrasound examinations performed annually (annual scan volume of the provider), duration of participation in the NTQR program, initial credentialing by an alternative pathway, provider type (physician vs sonographer) and number of NT-credentialed providers within the practice (size of practice). Each of these provider characteristics was evaluated for its effect on NT median MoM and geometric mean of the NT median MoM weighted for the number of ultrasound scans, and multiple regression was performed across all variables to control for potential confounders. RESULTS: Of 5 216 663 NT measurements from 9340 providers at 3319 sites, the majority (75%) of providers had an NT median MoM within the acceptable range of 0.9-1.1 and 85.5% had NT median MoM not statistically significantly outside this range. Provider characteristics associated with measurement within the expected range of performance included higher volume of NT scans performed annually, practice at a site with larger numbers of other NT-credentialed providers, longer duration of participation in the NTQR program and alternative initial credentialing pathway. CONCLUSIONS: Annual scan volume, duration of participation in the NTQR program, alternative initial credentialing pathway and number of other NT-credentialed providers within the practice are all associated with outcome metrics indicating quality of performance. It is critical that providers participate in ongoing quality assessment of NT measurement to maintain consistency and precision. Ongoing assessment programs with continuous feedback and education are necessary to maintain quality care. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Nuchal Translucency Quality Review (NTQR) program: first one and half million results.

OBJECTIVE: To evaluate the performance of first-trimester nuchal translucency (NT) measurement by providers (physician-sonologists and sonographers) within the Nuchal Translucency Quality Review (NTQR) program. METHODS: After training and credentialing providers, the NTQR monitored performance of NT measurement by the extent to which an individual's median multiple of the normal median (MoM) for crown-rump length (CRL) was within the range 0.9-1.1 MoM of a published normal median curve. The SD of log10 MoM and regression slope of NT on CRL were also evaluated. We report the distribution between providers of these performance indicators and evaluate potential sources of variation. RESULTS: Among the first 1.5 million scans in the NTQR program, performed between 2005 and 2011, there were 1 485 944 with CRL in the range 41-84 mm, from 4710 providers at 2150 ultrasound units. Among the 3463 providers with at least 30 scans in total, the median of the providers' median NT-MoMs was 0.913. Only 1901 (55%) had a median NT-MoM within the expected range; there were 89 above 1.1 MoM, 1046 at 0.8-0.9 MoM, 344 at 0.7-0.8 MoM and 83 below 0.7 MoM. There was a small increase in the median NT-MoM according to providers' length of time in the NTQR program and number of scans entered annually. On average, physician-sonologists had a higher median NT-MoM than did sonographers, as did those already credentialed before joining the program. The median provider SD was 0.093 and the median slope was 13.5%. SD correlated negatively with the median NT-MoM (r = -0.34) and positively with the slope (r = 0.22). CONCLUSION: Even with extensive training, credentialing and monitoring, there remains considerable variability between NT providers. There was a general tendency towards under-measurement of NT compared with expected values, although more experienced providers had performance closer to that expected.

Three-dimensional ultrasound detection of abnormally located intrauterine contraceptive devices which are a source of pelvic pain and abnormal bleeding.

OBJECTIVE: To determine whether intrauterine contraceptive devices (IUDs) that are located abnormally within the myometrium or cervix cause a higher incidence of pelvic pain and abnormal bleeding compared with normally positioned devices. METHODS: Over a period of 9 months, all patients with an IUD presenting at our unit for two-dimensional pelvic ultrasound underwent a three-dimensional (3D) volume reconstruction of the coronal view, to visualize the entire IUD within the cavity. The IUD was deemed malpositioned if any part extended past the cavity, into the myometrium or cervix. The indications for ultrasound were recorded at presentation for the exam. The presenting symptoms of patients with an abnormally located IUD were compared with those with normally positioned ones. RESULTS: Among 167 consecutive patients with an IUD evaluated using the 3D reconstructed coronal view, 28 (16.8%) had an IUD with side arms abnormally located within the myometrium. The abnormal positioning of the IUD arms was only detected using the 3D coronal view. A higher proportion of patients with an abnormally located IUD presented with bleeding (35.7%) or pain (39.3%) compared with those with normally positioned IUDs (15.1% with bleeding and 19.4% with pain) (P = 0.02 and 0.03, respectively). Seventy-five percent of patients with an abnormally located IUD presented with bleeding or pain compared with 34.5% of those whose IUD was normally placed (P = 0.0001). Twenty of 21 patients with an abnormally located IUD presenting with pelvic pain or bleeding reported improvement in their symptoms after IUD removal. CONCLUSION: A 3D coronal view of the uterus is useful in the visualization of IUDs. The coronal view showing the entire device and its position within the uterus may help in identifying the cause of pelvic pain and bleeding in patients with an embedded IUD.

Three-dimensional prenatal diagnosis of frontonasal malformation and unilateral cleft lip/palate.

Frontonasal malformation includes a spectrum of anomalies involving the eyes, nose, lips, forehead and brain. We present a case in which a fetal labial cleft was initially identified using traditional two-dimensional sonography. Three-dimensional sonography with multiplanar reconstruction and surface-rendering were essential to establish the diagnosis of frontonasal malformation with severe nasal hypoplasia and unilateral complete cleft lip/palate.

Variation in fetal femur length with respect to maternal race.

We sought to evaluate whether the expected fetal femur length, based on biparietal diameter, varies in second-trimester fetuses with respect to maternal race. The study population was composed of all fetuses scanned from 15 to 20 completed weeks' gestation during a 2-month period (June to August 1998). Maternal race was documented at the time of the ultrasonographic examination. Biparietal diameter and femur length were prospectively documented. The variance from the expected femur length, given the biparietal diameter, was calculated, and the mean variations were compared according to maternal race. The study subgroups were composed of the fetuses of 39 Asian mothers, 31 black mothers, and the first 100 white mothers. The mean values of the variance from the expected fetal femur length by biparietal diameter +/- 1 SD for the various racial groups were as follows: fetuses of Asian mothers, -0.66 +/- 1.64 mm; fetuses of black mothers, 0.88 +/- 1.57 mm; and fetuses of white mothers, 0.13 +/- 1.66 mm (P = .0007). To isolate the differences among the 3 racial groups, the mean values of the variance from the expected femur length by biparietal diameter for the fetuses of Asian and black mothers were compared with the mean value for the fetuses of white mothers (Asian versus white mothers, P = .014; black versus white mothers, P = .026). A significant difference in the mean variance from the expected femur length by biparietal diameter was identified among the fetuses of women in the second trimester with respect to racial group. Less-than-expected femur lengths were noted among the fetuses of Asian mothers, and greater-than-expected femur lengths were noted among the fetuses of black mothers, compared with the femurs of fetuses of white mothers. The implications for the use of fetal femur length as a component of the genetic sonogram in patients of various races require further study.

Isolated polydactyly: prenatal diagnosis and perinatal outcome.

Our objective was to determine the clinical significance of isolated polydactyly identified on prenatal sonogram. All patients with sonographically detected isolated polydactyly scanned over an 11-year period were identified from our database. All patients underwent detailed surveys, and follow-up was obtained by review of the medical records and telephone conversations with parents and referring physicians. Thirteen patients with isolated polydactyly were identified. Follow-up was available in 12 patients. Indications for referral included advanced maternal age (2), second-opinion polydactyly (4), family history of polydactyly (1), uncertain dates (5), and growth (1). The gestational ages at the times of sonographic diagnosis ranged from 17.5 to 34 weeks with all but one case being identified before 23 weeks. Prenatal identification included polydactyly of the upper limb (8), lower limb (4), and both upper and lower limbs (1). Postaxial polydactyly was seen in 12 patients and preaxial in one. Polydactyly was confirmed in all 12 cases in which follow-up was available. Karyotypes were normal in all five fetuses in which amniocentesis was performed. Ten of 12 fetuses were born alive, one died in utero at 34 weeks as a complication of severe pre-eclampsia and one died at term as a result of a cord accident. No surviving neonate had any other identifiable malformation or suspected karyotypic abnormality. In conclusion isolated polydactyly identified by prenatal sonography is associated with good perinatal outcome.

The frequency of the detection of fetal echogenic intracardiac foci with respect to maternal race.

OBJECTIVE: To determine if there is a racial difference in the frequency of identification of echogenic intracardiac foci (EIF) seen sonographically in the hearts of second-trimester fetuses. METHODS: Over a 2-month period (June 1998-August 1998), all fetuses scanned between 15 and 20 completed weeks' gestation were evaluated prospectively for the presence or absence of EIF. Pregnancies specifically referred for the presence of EIF were excluded. The sonographer performing the scan indicated maternal race as Asian, black, white, or (if maternal race was not clear) unknown. Maternal race, gestational age, and the presence or absence of EIF were prospectively documented. Follow-up of those fetuses with EIF was obtained from the referring physicians' offices. The groups were compared with respect to maternal race and presence or absence of EIF. RESULTS: There were 46, 34, 400, and nine fetuses of the Asian, black, white, and unknown mothers, respectively. The mean gestational age +/- 1 SD at examination was 18.2 +/- 1.6, 17.5 +/- 1.4, 17.7 +/- 1.5, and 17.8 +/- 1.1 weeks, for the Asian, black, white, and unknown mothers, respectively. The incidence of sonographically detected EIF was 30.4, 5.9, 10.5 and 11.1% for the Asian, black, white, and unknown mothers, respectively, P = 0.001. In a multivariate logistic regression model, Asian mothers had an odds ratio of 3.8 (95% CI, 1.8, 7.6) for having a fetus identified as having EIF, as compared with white mothers. CONCLUSIONS: The Asian patient is more likely than patients of other races to have a fetus with identified EIF. The counseling implications for Asian mothers undergoing midtrimester sonography when EIF is identified should be tempered, due to the increased frequency of EIF as a normal finding in the Asian population.

The prognostic significance of hyperextension of the fetal head detected antenatally with ultrasound.

OBJECTIVES: The purpose of this study was to evaluate the clinical significance of hyperextension of the fetal head detected by ultrasound prior to the onset of labour. METHODS: Over a 10-year period, we retrospectively identified all fetuses who had hyperextension of the fetal head reported on antenatal ultrasound. Hyperextension referred to persistence of the cervical spine in extreme extension, with an extension angle of at least 150 degrees persisting for the duration of the scan. Follow-up information was obtained from Hospital medical records and obstetrical care providers. RESULTS: Follow-up was obtained on 57 of the 65 fetuses (87.7%) identified over the study period. Ten of the 57 fetuses had normal structural fetal surveys and had sonographically identified resolution prior to delivery. All 10 patients delivered at term and had newborns with normal neonatal courses. Twenty-six of 57 fetuses had no sonographic findings other than persistent hyperextension, and 19 of these 26 fetuses (73%) had normal neonatal courses. Twenty-one of 57 fetuses (37%) had structural anomalies sonographically identified in addition to hyperextension of the fetal head. All 21 of these pregnancies ended in either termination or fetal or neonatal demize. CONCLUSIONS: Although resolution of isolated hyperextension of the fetal head is associated with a normal neonatal outcome, persistent isolated hyperextension of the fetal head can be associated with either a normal or an abnormal neonatal outcome. Fetuses with hyperextended heads and antenatally diagnosed structural anomalies have dismal outcomes. The identification of a fetus with hyperextension of the fetal head should prompt a detailed search for structural abnormalities.

Adenomyosis: sonographic findings and diagnostic accuracy.

The purposes of this study were to evaluate the accuracy of pelvic sonography in identification of adenomyosis and to characterize the most commonly seen sonographic features. We identified all patients over a 10 year period in whom a prospective diagnosis of adenomyosis was suspected on the basis of sonographic findings and who had undergone hysterectomy at a single hospital. Patients were referred for sonography based on standard indications. Sonographic features used in the diagnosis of adenomyosis consisted of two or more of the following: a mottled inhomogeneous myometrial texture, globular appearing uterus, small cystic spaces within the myometrium, and a "shaggy" indistinct endometrial stripe. Correlation was made with the pathology report on the hysterectomy specimen. Fifty-one women met the study criteria. Forty-three of 51 (84.3%) patients sonographically suspected of having adenomyosis were confirmed as having adenomyosis by pathologic examination. All patients with adenomyosis had a mottled heterogeneous appearing uterus, 95% had a globular uterus, 82% had small myometrial lucent areas, and 82% had an indistinct endometrial stripe. Eight patients (15.6%) who had been suspected of having adenomyosis by pelvic sonography did not have adenomyosis reported in the pathology specimen. Six of these eight (75%) patients had multiple small fibroids, one had stage IV endometriosis, and one had a normal uterine specimen with no evidence of pathology. Pelvic sonography provides an accurate diagnosis of adenomyosis in the majority of cases.

Is a full bladder still necessary for pelvic sonography?

The objective was to determine whether a full bladder is routinely necessary for a complete sonographic evaluation of the female pelvis. Over the course of 1 month, all women having a gynecologic sonogram were scanned initially transabdominally through a full bladder by the sonographer (standard images taken). A physician then joined the sonographer and scanned the patient transvaginally without prior knowledge of the findings seen transvesically. The physician finished the examination transabdominally, with the bladder empty. The physician and sonographer then determined (1) whether the scan was sufficient transvaginally only, (2) whether the scan was sufficient transvaginally and transabdominally with an empty bladder, or (3) or whether a full bladder was necessary. Two hundred and six consecutive patients were scanned prospectively. The transvaginal scan alone was sufficient to demonstrate all findings for 172 (83.5%) patients. The transvaginal and transabdominal scans through an empty bladder were needed for 31 (15.1%) patients. Three patients (1.5%) required a full bladder in addition to the other two techniques to visualize one normal ovary each. In conclusion, transvaginal scanning with an adjunctive transabdominal empty bladder approach can replace the full bladder technique for routine pelvic sonography. The transabdominal scan with an empty bladder is necessary, particularly for patients with enlarged uteri. It is no longer reasonable, however, to subject all patients undergoing pelvic sonography to bladder distention.

The sonographic diagnosis of Dandy-Walker and Dandy-Walker variant: associated findings and outcomes.

Outcomes of pregnancies with sonographically diagnosed Dandy-Walker (DW) or Dandy-Walker variant (DWV) syndromes vary widely. We examined our own experience with these diagnoses in an effort to identify those sonographic features that best predicted neonatal outcome. We identified 50 fetuses with DW and 49 with DWV diagnosed sonographically. Eighty-six per cent of fetuses with DW and 85% of fetuses with DWV had other sonographically identifiable anomalies, the most common being ventriculomegaly (DW: 32%; DWV: 27%) and cardiac defects (DW:38%; DWV: 41%). Forty-six per cent and 36% of available karyotypes in cases of DW and DWV, respectively, were abnormal. 50 out of 99 women in our series elected pregnancy termination. Only three pregnancies with DW resulted in a living infant, and only one of these had a normal paediatric examination at six-week follow-up. Thirteen out of 49 infants with DWV survived the neonatal period and 7 of 13 were reported initially as normal infants, including six with an isolated finding of DWV. We conclude that overall, the prognosis for these posterior fossa defects is grim but not uniformly fatal. The presence of other anomalies is associated with the worst prognosis. Isolated Dandy-Walker variant has the highest chance of leading to a normal neonate.

Aicardi syndrome: prenatal sonographic findings. A report of two cases.

The prenatal sonographic findings in two children with Aicardi syndrome are reported.

Amnion-chorion separation after 17 weeks' gestation.

OBJECTIVE: To evaluate the cause of and perinatal outcomes of amnion-chorion separation that is apparent sonographically after 17 weeks' gestation. METHODS: We searched our ultrasound database over 7 years for information on pregnant women who had live fetuses and complete separation between amnion and chorion that persisted beyond 17 weeks' gestation. For inclusion in the study, the women had to have amnion separated from chorion on at least three sides of the gestational sac. Medical records were reviewed for whether women had amniocenteses, results of the amniocenteses, and outcomes of the pregnancies. RESULTS: Of 15 pregnant women with live fetuses, ten had amniocenteses before identification of amnion-chorion separation and five did not. Three had fetuses with Down syndrome, two of whom had amnion-chorion separation evident before amniocentesis, and all three had other sonographic findings suggestive of aneuploidy. Three fetuses died. The other pregnancies were complicated by one or more adverse events, including two fetuses with growth restriction, five preterm deliveries, two with oligohydramnios, and one with abruptio placentae. Five infants were delivered at term and are alive and well. Overall, ten of 15 pregnancies resulted in live newborns, one of whom had Down syndrome. CONCLUSION: Complete amnion-chorion separation that persisted after 17 weeks' gestation is associated with a variety of adverse perinatal outcomes, including aneuploidy.

Genetic sonogram scoring index: accuracy and clinical utility.

We sought to evaluate the accuracy of the genetic sonogram scoring index in detecting Down syndrome fetuses in a high-risk population. Women referred for genetic sonogram scoring index based on increased risk for aneuploidy were prospectively evaluated. Each fetus was assigned a score based on our previously published genetic sonogram scoring index. A score of 1 or greater was an indication for karyotype determination. Of 1076 patients (1118 fetuses) in the study group, follow-up data were available for 1030 (92%), eight of whom had Down syndrome (prevalence 0.8%). Three fetuses with Down syndrome had a genetic sonogram scoring index of 0, and for one of these the mother was 42 years old. One affected fetus had a score of 1 and the other four had scores of 2 or greater. Using a genetic sonogram scoring index of 1 or greater (age not considered), five of eight fetuses with Down syndrome (62.5%) were identified, as well as 150 of 1030 (14.6%) of normals. Down syndrome was undetected in three fetuses of 1030 (1 in 343) or 0.29%. In addition, when all women 40 years old or older underwent karyotype testing regardless of their sonographic findings, six of eight Down syndrome fetuses were identified (75%), as well as 271 of 1030 (26.3%) of normals. The number of cases of Down syndrome not detected was two in 1030 (1 in 515) or 0.19%. In conclusion, the genetic sonogram scoring index was used to identify approximately 75% of fetuses with Down syndrome, with amniocentesis being recommended in 26.7% of a high-risk population.

Does the 10-MHz transvaginal transducer improve the diagnostic certainty that an intrauterine fluid collection is a true gestational sac?

PURPOSE: We studied whether a 10-MHz transvaginal transducer improves the diagnostic certainty that a small intrauterine fluid collection is a true gestational sac. METHODS: Over a 6-week period, women who presented with a positive pregnancy test and a fluid collection (devoid of any characteristics such as yolk sac or fetal pole) in the uterus seen with a standard 6-7-MHz transvaginal transducer were entered in the study. The patients were immediately rescanned with a 10-MHz transvaginal probe, and characteristics of the fluid collection using this probe were noted. Specifically, the visualization of a yolk sac or the intradecidual or double decidual sign was considered an objective improvement in the certainty that the fluid collection was a gestational sac. RESULTS: Twelve patients presented with a positive pregnancy test and a fluid collection in the uterus seen with a 6-7-MHz probe. Eight of these fluid collections were smaller than 1 cm in mean diameter, and all 8 of these patients had an objective improvement in the diagnosis of an intrauterine pregnancy using the 10-MHz probe. The other 4 patients had fluid collection 1-2 cm in mean diameter seen at 6-7 MHz. The 10-MHz probe improved the diagnostic confidence in 2 of these 4 patients. CONCLUSIONS: In patients with early pregnancies who have questionable gestational sacs on sonography with standard 6-7-MHz transducers, the 10-MHz probe improves the diagnostic confidence of the presence of an intrauterine gestational sac.

The second-trimester fetal iliac angle as a sign of Down's syndrome.

OBJECTIVE: To determine whether the iliac angle of second-trimester fetuses is a useful sonographic marker for the detection of fetuses with Down's syndrome. METHODS: We prospectively measured the iliac angle for all fetuses karyotyped over a 17-month period. A transverse view of the upper fetal pelvis was obtained at the time of amniocentesis and, by means of a protractor, the angle between the two iliac bones was measured. The angles of all those fetuses with Down's syndrome and the first 500 fetuses with normal karyotypes were compared, as was gestational age and maternal age. RESULTS: Nineteen fetuses with Down's syndrome and 1167 fetuses with normal karyotypes underwent genetic amniocentesis over the study period. The mean gestational age of the fetuses with Down's syndrome was 16.6 weeks (+/- 1.9 weeks), and for the controls, 16.1 weeks (+/- 1.4 weeks) (p = 0.3). The mean maternal ages were 34.7 years (+/- 4.8 years) and 35.4 years (+/- 4.1 years) for those pregnancies with Down's syndrome and with normal karyotypes, respectively (p = 0.5). The mean iliac angle was 80.1 degrees (+/- 19.7 degrees) for those fetuses with Down's syndrome, and 63.1 degrees (+/- 20.3 degrees) for those fetuses with normal karyotypes (p = 0.0004). The iliac angle was at least 90 degrees in 36.8% (seven of 19 fetuses) with Down's syndrome and in 12.8% (64 of 500 fetuses) with normal karyotypes (p = 0.003). CONCLUSION: Fetuses with Down's syndrome have a significantly larger iliac angle than fetuses with normal karyotypes. Use of an iliac angle cut-off point of 90 degrees would identify over one-third of second-trimester fetuses with Down's syndrome. However, because of the high false-positive rate (12.8%), the iliac angle is not useful in a high-risk population as a screening test when used in isolation.