The antenatal diagnosis of placenta accreta.

The incidence of placental attachment disorders continues to increase with rising caesarean section rates. Antenatal diagnosis helps in the planning of location, timing and staffing of delivery. In at-risk women grey-scale ultrasound is quite sensitive, although colour ultrasound is the most predictive. Magnetic resonance imaging can add information in some limited instances. Patients who have had a previous caesarean section could benefit from early (before 10 weeks) visualisation of the implantation site. Current data refer only to placentas implanted in the lower anterior uterine segment, usually over a caesarean section scar.

Comparison of cardiac Z-score with cardiac asymmetry for prenatal screening of congenital heart disease.

OBJECTIVE: To determine the best screening tests for discriminating early indicators of cardiac hypoplasia in congenital heart disease (CHD) from normal variations in fetal cardiac growth. METHODS: We retrospectively examined fetal echocardiograms from 90 infants with confirmed CHD: Group 1 (n = 35) with right-sided obstructive lesions and Group 2 (n = 55) with left-sided obstructive lesions. Our control group comprised 2735 normal fetuses, from which we determined fetal cardiac Z-scores of right ventricle (RV), left ventricle (LV), aorta (Ao) and pulmonary artery (PA) diameters and ratios of right to left ventricle (RV:LV) and pulmonary artery to aorta (PA:Ao) size. We compared our control group to Groups 1 and 2 using ANOVA and area under receiver-operating characteristics curve (AUC) analysis. RESULTS: For Group 1, RV:LV ratio, RV-Z-score and PA:Ao ratio were the best screening tests, with highest AUCs (0.879, 0.868 and 0.832, respectively). For Group 2, the Ao-Z-score, PA:Ao and RV:LV ratios were the best screening tests, with AUCs of 0.770, 0.723 and 0.716, respectively. CONCLUSION: None of the screening tests was found to be a perfect early discriminator for the cardiac lesions tested. Although ratios of PA:Ao and RV:LV are useful, they should be combined with fetal cardiac Z-scores to maximize screening sensitivity.

Fetal echocardiography: z-score reference ranges for a large patient population.

OBJECTIVES: The main goal was to develop new z-score reference ranges for common fetal echocardiographic measurements from a large referral population. METHODS: A retrospective cross-sectional study of 2735 fetuses was performed for standard biometry (biparietal diameter (BPD) and femoral diaphysis length (FDL)) and an assessment of menstrual age (MA). Standardized fetal echocardiographic measurements included aortic valve annulus and pulmonary valve annulus diameters at end-systole, right and left ventricular diameters at end-diastole, and cardiac circumference from a four-chamber view of the heart during end-diastole. Normal z-score ranges were developed for these echocardiographic measurements using MA, BPD and FDL as independent variables. This was accomplished by using first standard regression analysis and then weighted regression of absolute residual values for each parameter in order to adjust for inconstant variance. RESULTS: A simple, linear regression model was the best description of the data in each case and correlations between fetal cardiac measurements and the independent variables were excellent. There was significant heteroscedasticity of standard deviation with increasing gestational age, which also could be modeled with simple linear regression. After this adjustment, the residuals conformed to a normal distribution, validating the calculation and interpretation of z-scores. CONCLUSION: Development of reliable z-scores is possible for common fetal echocardiographic parameters by applying statistical methods that are based on a large sample size and weighted regression of absolute residuals in order to minimize the effect of heteroscedasticity. These normative ranges should be especially useful for the detection and monitoring of suspected fetal cardiac size and growth abnormalities.

Maintaining quality assurance for sonographic nuchal translucency measurement: lessons from the FASTER Trial.

OBJECTIVE: To evaluate nuchal translucency measurement quality assurance techniques in a large-scale study. METHODS: From 1999 to 2001, unselected patients with singleton gestations between 10 + 3 weeks and 13 + 6 weeks were recruited from 15 centers. Sonographic nuchal translucency measurement was performed by trained technicians. Four levels of quality assurance were employed: (1) a standardized protocol utilized by each sonographer; (2) local-image review by a second sonographer; (3) central-image scoring by a single physician; and (4) epidemiological monitoring of all accepted nuchal translucency measurements cross-sectionally and over time. RESULTS: Detailed quality assessment was available for 37 018 patients. Nuchal translucency measurement was successful in 96.3% of women. Local reviewers rejected 0.8% of images, and the single central physician reviewer rejected a further 2.9%. Multivariate analysis indicated that higher body mass index, earlier gestational age and transvaginal probe use were predictors of failure of nuchal translucency measurement and central image rejection (P = 0.001). Epidemiological monitoring identified a drift in measurements over time. CONCLUSION: Despite initial training and continuous image review, changes in nuchal translucency measurements occur over time. To maintain screening accuracy, ongoing quality assessment is needed.

First- and second-trimester Down syndrome screening markers in pregnancies achieved through assisted reproductive technologies (ART): a FASTER trial study.

OBJECTIVE: To determine whether first- and second-trimester Down syndrome screening markers and screen-positive rates are altered in pregnancies conceived using assisted reproductive technologies (ARTs). METHODS: ART pregnancies in the multicenter FASTER trial were identified. Marker levels were evaluated for five types of ART: in vitro fertilization with ovulation induction (IVF-OI), IVF with OI and egg donation (IVF-OI-ED), IVF with ED (IVF-ED), and intrauterine insemination with OI (IUI-OI) or without OI (IUI). Each group was compared to non-ART controls using Mann-Whitney U analysis. RESULTS: First-trimester marker levels were not significantly different between ART and control pregnancies, with the exception of reduced PAPP-A levels in the IUI-OI group. In contrast, second-trimester inhibin A levels were increased in all ART pregnancies, estriol was reduced and human chorionic gonadotropin (hCG) was increased in IVF and IUI pregnancies without ED, and alpha-fetoprotein (AFP) was increased in ED pregnancies. Second-trimester screen-positive rates were significantly higher than expected for ART pregnancies, except when ED was used. CONCLUSIONS: These data show that ART significantly impacts second-, but not first-, trimester markers and screen-positive rates. The type of adjustment needed in second-trimester screening depends on the particular type of ART used.

Antenatal diagnosis of placenta accreta: a review.

The incidence of placenta accreta should rise steadily over the next century as the frequency of Cesarean sections and advanced maternal age, both independent risk factors, increases. Patients who are at risk should be identified before an ultrasound examination and the characteristic findings searched for. In the first trimester, these include a low-lying sac that appears to be attached to the anterior wall of the uterus. As early as 16 weeks irregular vascular sinuses appear, which have turbulent flow within. The bladder wall may appear interrupted or have small bulges of the placenta into the bladder space. Absence of the normal echolucent space between the placenta and myometrium is not a reliable sign by itself, since this space may be absent in normal patients with an anterior placenta. Color Doppler will show that some of the placental sinuses traverse the uterine wall. Magnetic resonance imaging has not yet been shown to aid in the diagnosis, but in the future, with improvement of resolution and shortened sequences, it should be particularly useful in identifying the patients that have placenta percreta.

Prenatal closure of abdominal defect in gastroschisis: case report and review of the literature.

With the routine use of fetal imaging studies during prenatal care, increased numbers of unusual intrauterine events are now detected. Prenatal closure of the abdominal defect in gastroschisis is an example. We report a 34 5/7-week stillborn who had prenatal closure of a ventral abdominal wall defect, which had been seen earlier on fetal ultrasound examination. Two ultrasound examinations performed at 15 1/7 weeks and 19 1/7 weeks showed a mass of exteriorized bowel that herniated through the abdominal defect, just to the right of the umbilical cord. At 30 1/7 weeks, no exteriorized bowel was seen, but thickened and dilated intraabdominal bowel was identified. No abdominal defect or exteriorized bowel was found at autopsy. There was a severely dilated proximal jejunum with the absence of the rest of the small intestine and the right side of the colon. The remaining left side of the colon was small and blind proximally. Six similar isolated examples have been reported since 1991. Prenatal closure of an abdominal defect was associated with long-segment atresia of the midintestine in each case. We believe that the spontaneous closure of this abdominal defect was associated with atresia and resorption of exteriorized bowel. It is likely some of the cases of long-segment atresia may in fact be associated with closed gastroschisis.

What to expect from routine midtrimester screening for congenital heart disease.

The four-chamber view is the standard screening view of the fetal heart. However, it detects only about half of cardiac defects. Because this view does not show the great vessels, only conotruncal abnormalities with substantial septal defects will be seen. Second, septal defects may be too small at the time of screening to be detected. In addition, some defects such as pulmonic stenosis are late appearing. The addition of the aortic outflow tract view increases sensitivity by approximately 20%. Although all components of the four-chamber view may not be seen, there is still considerable information supplied by each of its parts.

Vasa previa: prenatal diagnosis, natural evolution, and clinical outcome.

OBJECTIVE: To describe the prenatal ultrasonographic diagnosis, natural evolution, and clinical outcomes of vasa previa in a large population at a single institution. METHODS: We attempted to view the internal cervical os of 93,874 women with second- and third-trimester pregnancies during an 8-year period. Echogenic parallel or circular lines near the cervix, seen by gray-scale ultrasonography, raised the possibility of vasa previa. Diagnosis was confirmed by Doppler and endovaginal studies if aberrant vessels over the internal cervical os were suspected. Abnormal placental morphology and velamentous cord insertion were documented if they were identified during prenatal scans. Ultrasonographic findings were correlated with clinical courses, perinatal outcomes, and placental pathology examinations. RESULTS: Eighteen cases of vasa previa were suspected at a mean (+/- standard deviation) gestational age of 26.0 +/- 6.3 weeks; the earliest diagnosis was at 15.6 weeks' gestation. Eight of those cases initially showed placental edge over the internal os and later developed vasa previa after the placenta "receded" from the cervix. Six women had mild vaginal bleeding at a mean gestational age of 31.3 weeks. Three women had normal late third-trimester scans and were allowed to have uncomplicated vaginal deliveries. The remaining subjects delivered by cesarean. There were two deaths (one fetal and one neonatal), and minor preterm complications slightly prolonged infant hospitalizations. One set of preterm twins needed neonatal transfusions. Pathology findings included ten cases of velamentous insertion and three cases each of bilobed placentas, succenturiate lobes, and marginal cord insertion. CONCLUSION: Vasa previa was detected in asymptomatic women as early as the second trimester. Perinatal outcome was generally favorable, although several infants had slightly extended newborn nursery admissions due to mild complications of prematurity.

Fetal cleft lip and palate detection by three-dimensional ultrasonography.

OBJECTIVES: To demonstrate a standardized approach for the evaluation of cleft lip and palate by three-dimensional (3D) ultrasonography. DESIGN: This was a retrospective study of seven fetuses with confirmed facial cleft anomalies. Post-natal findings were compared to a blinded review of 3D volume data from abnormal fetuses with seven other normal fetuses that were matched for gestational age. Upper lip integrity was examined by 3D multiplanar imaging. Sequential axial views were used to evaluate the maxillary tooth-bearing alveolar ridge contour and anterior tooth socket alignment. Alveolar ridge disruption suggested cleft palate. Premaxillary protrusion, either by multiplanar imaging or surface rendering, indicated bilateral cleft lip and palate. RESULTS: Post-natal findings confirmed bilateral cleft lip and palate (four cases), unilateral cleft lip and palate (one case), and unilateral cleft lip (two cases). Multiplanar review identified all three fetuses with unilateral cleft lip, three of four fetuses with bilateral cleft lip, one fetus with unilateral cleft palate, and three of four fetuses with bilateral cleft palate. Surface rendering correctly identified all cleft lips, with the exception of one fetus, who was thought to have a unilateral cleft lip and palate, despite the actual presence of a bilateral lesion. One cleft palate defect was directly visualized by 3D surface rendering. No false-positives occurred. CONCLUSION: Interactive review of standardized 3D multiplanar images allows one to evaluate labial defects, abnormalities of the maxillary tooth-bearing alveolar ridge, and presence of premaxillary protrusion for detecting cleft lip and palate anomalies. Surface rendering may increase diagnostic confidence for normal or abnormal studies. This technology provides an array of visualization tools that may improve the prenatal characterization of facial clefts, particularly of the palate.

Vasa previa: prenatal detection by three-dimensional ultrasonography.

OBJECTIVE: To describe three-dimensional (3D) ultrasonography (US) for the antepartum diagnosis of vasa previa. DESIGN: This was a descriptive study of two pregnant women who were suspected to have vasa previa by conventional gray-scale ultrasonography. Three-dimensional studies were also performed during the early third trimester to further investigate the possibility of this condition. RESULTS: In the first case, 3D US provided gray-scale multiplanar and surface-rendered views of an aberrant vessel over the internal cervical os. For the second case, a 'flight-path' technique allowed the examiner to follow axial views of the endocervical canal toward the internal os until an aberrant vessel was verified. The 'niche-mode' analysis, with and without color power Doppler ultrasonography, was also used to confirm the diagnosis. CONCLUSION: Three-dimensional ultrasonography offers several additional imaging tools that are not currently provided by more conventional ultrasonography for the detection of vasa previa. It represents an important adjunct to two-dimensional (2D) studies, especially when this diagnosis is questionable.

Central nervous system anomalies.

Fetal central nervous system abnormalities encompass a variety of lesions. Most of the anomalies are seen in association with an increased incidence of fetal aneuploidy and an increase in other anomalies both within and outside of the central nervous system. These associated findings and the underlying lesion all have a role in the eventual prognosis for the ongoing pregnancy. The antenatal diagnosis of a central nervous system abnormality should prompt a careful search for other defects, and consideration should be given for genetic evaluation and testing.

Fetal cardiac asymmetry: a marker for congenital heart disease.

OBJECTIVE: To determine the sensitivity of prenatally detected fetal cardiac asymmetry as a sonographic marker for congenital heart disease. METHODS: The normal ratios of pulmonary artery to aorta diameters and of right ventricle to left ventricle diameters were derived from normal fetuses scanned at 17 weeks or more in a 65-month period. Cross-sectional diameters of cardiac ventricles and great arteries were measured at the level of the valves at the time of the scan. Fetuses with confirmed cardiac anomalies detected prenatally during the study were examined to identify how many had cardiac asymmetry, determined by abnormal ratios. RESULTS: Linear regression analysis of the group of 881 normal fetuses showed the normal pulmonary artery to aorta diameter ratio remained constant throughout pregnancy and the normal right ventricle to left ventricle ratio increased slightly with progressing gestational age. The 90% confidence intervals were 0.79, 1.24 for the right ventricle to left ventricle ratio and 0.84, 1.41 for the pulmonary artery to aorta ratio. Of the 73 fetuses with abnormal hearts, 66% had either ventricular or great artery asymmetry (at least one of the two ratios was abnormal). However, if no asymmetry was present, the cardiac defect was more likely to be a minor one. CONCLUSION: Cardiac asymmetry was present in two-thirds of fetuses with cardiac anomalies diagnosed prenatally. If cardiac asymmetry is found, a more thorough examination of the fetal heart is indicated.

Double-outlet right ventricle: an antenatal diagnostic dilemma.

OBJECTIVE: The purpose of this study was to describe the antenatal ultrasonographic findings of fetuses with double-outlet right ventricle (DORV). DESIGN: The records were reviewed of all fetuses scanned in our ultrasound unit which were suspected of having DORV during a 6-year period ending in April 1996. A medical record search for all infants with a postnatal diagnosis of DORV was also undertaken to identify cases that were not detected antenatally. Records were examined to determine the accuracy of antenatal diagnosis and the reasons for diagnostic errors. Fetuses without follow-up were excluded. RESULTS: There were 20 fetuses with antenatally detected conotruncal defects that had DORV included in the differential diagnosis. Three fetuses were excluded, seven did not have DORV and ten were confirmed postnatally as having DORV. Two additional infants were found to have DORV from the medical record search, producing a total of 12 cases. Antenatal sonographic cardiac findings included malpositioned (overriding or transposed) great arteries (n = 11), ventricular septal defect (n = 11) and small pulmonary artery suggesting stenosis (n = 4). Confirmed postnatal cardiac findings that were missed antenatally included aortic coarctation (n = 2), right-sided aortic arch (n = 2) and pulmonary stenosis (n = 1). Seven of the 12 fetuses had extracardiac findings. Nine of the 12 fetuses tested had a normal karyotype. Eleven of the 12 infants were liveborn. Nine of these 11 survived the neonatal period and underwent surgical repair within the first year of life; two subsequently died. In total, seven fetuses survived and five did not. CONCLUSIONS: Most fetuses with DORV can be identified antenatally as having an abnormal heart. However, it is very difficult to distinguish this particular defect from other conotruncal abnormalities.

Right fetal cardiac axis: clinical significance and associated findings.

OBJECTIVE: To ascertain the clinical significance of right fetal cardiac axis. METHODS: Fetal cardiac axis was assessed prospectively in ultrasound examinations of 16,562 fetuses over a 6-year period. RESULTS: Twenty-two fetuses had a right cardiac axis. When classified by ventricular and atrial configuration, six fetuses had mirror-image hearts with situs inversus, 12 had rotation of the heart axis alone, and four had inversion of the ventricles. Fourteen of the 22 had underlying structural cardiac defects, most of which were atrioventricular septal defects, double outlet right ventricles, or common atria. The chromosomes and/or phenotypes of all 22 were normal. All four fetuses with polysplenia and asplenia died. Major extracardiac defects were few (two) but lethal. CONCLUSION: Right cardiac axis in the fetus is associated with a high incidence of structural cardiac defects. In the absence of severe extracardiac defects, polysplenia, or asplenia, neonatal outcome was good.

Birthweight prediction by three-dimensional ultrasonographic volumes of the fetal thigh and abdomen.

Our validation study examined a three-dimensional ultrasonographic phantom that contained irregularly shaped volume targets ranging from 0.5 to 76.1 milliliters. Four different examiners made blinded measurements from volume datasets that were acquired by 4 and 7 MHz transducers. Birthweight predictions using abdominal and thigh volumes from 18 term fetuses also were compared with two-dimensional ultrasonographic methods. In vitro volume measurements were accurate, precise, and repeatable despite a small systematic overestimation with increasing object size. Mean systematic error and precision for birthweight predictions by three-dimensional ultrasonography (-0.03% +/- 6.1%) were not significantly different from those by two-dimensional ultrasonography (-0.60% +/- 8.8%). Conventional prediction methods yielded three birthweights with greater than 15% error. By comparison, except for one infant whose birthweight indicated an 11% error, all predictions based on fetal volume parameters were within 10% of true values. Accurate birthweight predictions by fetal volume parameters appear to be technically feasible at term gestation although their practical clinical application requires further investigation. Birthweight predictions in this manner may allow remote consultants to evaluate the fetus over wide-area computer networks despite the physical absence of the patient.