Comparison of noninvasive prenatal screening with combined first-trimester screening as a frontline screening approach for common trisomies in a public hospital in Australia

BACKGROUND

Combined first-trimester screening (cFTS) for fetal anomalies involves maternal serum screening for biochemical markers and measurement of the nuchal translucency (NT) by ultrasound. Noninvasive prenatal screening (NIPS) analyses cell-free DNA present in a maternal blood sample for presence of fetal chromosomal aneuploidies.

AIMS

To compare NIPS with cFTS as frontline screening in a public hospital in Australia.

MATERIALS AND METHODS

Women were offered NIPS in addition to the usual cFTS routinely offered to all women at a public hospital in NSW, Australia. The cFTS sample was collected at ten weeks' gestation and the NIPS sample at 12 weeks' gestation at the ultrasound appointment.

RESULTS

In a low-risk population of 997 women, frontline NIPS had a screen-positive rate of 0.5% (5/997) vs 4.2% (42/997) with cFTS. cFTS correctly identified one trisomy 21 case and one trisomy 18 case; however, there were two trisomy 18 false negatives. Of five positive NIPS calls, four were correctly identified as trisomy 21 (one) and trisomy 18 (three); there were no NIPS false negatives. Overall, the false-positive rate with NIPS was 0.1% vs 4.0% by cFTS.

CONCLUSIONS

The lower screen-positive rate with NIPS for common trisomies was a result of the significantly lower false-positive rate with NIPS. Consequently, NIPS as first-line screening, even if funded by the hospital, may provide cost savings. We believe NIPS should be used from ten weeks' gestation in conjunction with morphology ultrasound for routine first-trimester prenatal management.

Screening the second-trimester fetal heart in women with an increased body mass index using three-dimensional volume sweep

PURPOSE

To determine the percentage of fetal cardiac anatomy as detailed in the International Society of Ultrasound in Obstetrics and Gynecology Practice Guidelines on sonographic screening examination of the fetal heart, which can be visualised in women with a body mass index (BMI) >30 kg/m² using three-dimensional (3D) volume sweeps.

METHODS

3D volumes of the fetal heart were taken prospectively in 40 fetuses during routine second-trimester fetal anatomy scan. Scans and 3D volume sweeps were performed by two experienced sonographers and two experienced raters interpreted the 3D data. 3D volume acquisitions and post-processing analysis were performed according to the techniques described by Weissmann-Brenner et al.

RESULTS

The two raters were able to detect an average of 12.9 and 14.1 of the 16 parameters in the 40 patients. Agreement between raters for the 16 parameters had an average of 80%. Five parameters (stomach, situs, heart occupies a third of thoracic area, majority of heart in the left chest and cardiac axis) were detected by both raters on all patients. The range of agreement was between 40% and 100%. The three-vessel view and bifurcation had agreement <60%.

CONCLUSION

Consistent identification of all views of the fetal heart was not achieved using the simple method described in women with a BMI > 30 kg/m².

Maternal abdominal subcutaneous fat thickness as a predictor for adverse pregnancy outcome: a longitudinal cohort study

OBJECTIVE

To assess maternal abdominal subcutaneous fat thickness (SFT) measured by ultrasound as an independent predictor of adverse pregnancy outcomes.

DESIGN

A prospective longitudinal cohort study performed on pregnancies delivered between 2012 and 2014.

SETTING

Sydney, Australia.

POPULATION

About 1510 pregnant women attending routine obstetric ultrasounds.

METHODS

Maternal SFT was measured on routine ultrasounds at 11-14 weeks' gestation (SFT1) and 18-22 weeks' gestation (SFT2). SFT measurements were assessed for estimating risks for obesity-related pregnancy outcomes using logistic regression modelling adjusted for maternal age, parity, smoking status and body mass index (BMI).

MAIN OUTCOME MEASURES

Hypertensive disease, gestational diabetes, caesarean section, low birthweight, preterm delivery, neonatal respiratory distress, Apgar scores, and admission to a neonatal intensive care unit.

RESULTS

SFT1 and SFT2 were measured on 1461 and 1363 women, respectively. Mean thickness (range) were 21.2 mm (6.9-73.9) for SFT1 and 20.3 mm (7.5-68.0) for SFT2. Complete outcome data were available for 1385 pregnancies. In all, 54% of the women were overweight/obese. The SFT measures decreased from early to mid-pregnancy in overweight/obese women. There was moderate correlation between BMI and SFT1 (R(2) = 0.56) and BMI and SFT2 (R(2) = 0.55). In a multivariate model, SFT1 and SFT2 were better predictors for adverse pregnancy outcomes than BMI.

CONCLUSION

Maternal SFT is a significant independent predictor of adverse pregnancy outcomes. Incorporation of SFT into future models for adverse pregnancy outcome may prove valuable.

A futuristic vision of pocket ultrasound machines: watch this space

Introduction: Australian medical ultrasound started in 1959 with the establishment of the Ultrasonics Institute. Since then the technology has advanced tremendously. We are now not only able to obtain clearer images on high specification ultrasound machines but also on pocket‐sized ultrasound machines that are compact, lightweight and affordable.

Method: The following descriptive review will examine the indication for use of pocket ultrasound machines in different clinical settings as well as provide evidence of its image clarity and accuracy. Potentially eligible studies were sought primarily through searches of the electronic databases PubMed, Medline (1996–Present), Embase (1996–Present) and Cochrane Library.

Conclusion: Pocket ultrasound machines, with appropriate ultrasound knowledge and training, can be incorporated successfully in patient management. The addition of point‐of‐care ultrasound has been shown to improve management recommendations and outcomes.

Sonographic diagnosis of spontaneous uterine rupture at the site of cornual wedge resection scar - a case report

Introduction: Uterine rupture and uterine dehiscence during pregnancy are known complications of a scarred uterus. Spontaneous uterine rupture at the site of prior cornual wedge resection has been previously reported in the literature, however remains rare.

Discussion: We present a case of uterine rupture at 30 weeks gestation. This woman had previous right sided interstitial pregnancy treated with uncomplicated laparoscopic cornual wedge resection at eight weeks gestation. The index pregnancy occurred eight months after surgery. An emergency ultrasound prompted by non‐specific abdominal pain and tenderness at 30 weeks gestation enabled diagnosis of uterine dehiscence. At emergency caesarean section four hours later full thickness wall rupture and haemoperitoneum were found. Surgical intervention resulted in a good outcome for both mother and baby.

Conclusion: A brief account on uterine rupture in late pregnancy and relevant sonographic features related to this case are presented. This case demonstrates the value of ultrasound in the assessment of subtle clinical signs and symptoms in patients at risk of uterine rupture.

The effect of preliminary training on quantitative evaluation of sonographer performance in the fetal morphology ultrasound examination

Introduction: The aim of this study is to provide a quantitative scoring system to assess sonographer performance by reviewing images from the fetal morphology examination.

Methods: Ten ultrasound images from patients at 18–22 weeks gestation were assessed and scored for quality according to predefined criteria. One hundred normal cases were randomly selected and 10 images from each case were analysed by four experienced reviewers. The preliminary training incorporated the first 25 cases and involved a training period for reviewers; the remaining 75 cases were allocated to post training. The scores acquired by each reviewer were statistically analysed using Pearson's and intra‐class correlations to determine the reproducibility of the results.

Results: The preliminary training results were calculated separately and compared to the post training study. The preliminary intra‐class correlation coefficient was 0.12. In the post training study the intra‐class correlation coefficient was doubled at 0.24. The greatest correlation was observed between reviewers 1 and 4 with a coefficient of 0.71. Reviewers 3 and 4 demonstrated the lowest correlation coefficient of 0.30.

Discussion: A significant increase in the intra‐class correlation coefficient indicated that training reviewers achieves more reproducible results. Suggested improvements to the study include recording fetal position, maternal BMI and assessing individual reviewer variability. An instruction manual defining each criterion might also yield better results.

Conclusion: The quantitative method used in this study assessed ultrasound images by placing a numerical value on image quality. Analysis of the preliminary training period demonstrates improved reproducibility of the results. Further investigation into the criteria is necessary to refine the quantitative method.

The K-P algorithm: a new first-trimester growth model - comparison with other formulae and correlations with recorded embryonic lengths

OBJECTIVE

To generate and validate individually fitted first-trimester growth curves using a new growth model. Secondary aims were to compare this new model with actual recorded embryonic measurements and validate its predictive accuracy.

METHODS

A prospective study of women presenting to the Early Pregnancy Unit in the first trimester. Women with viable singleton pregnancies at the end of the first trimester who had had at least two crown-rump length (CRL) measurements were selected. An individual power function of CRL was derived from serial CRL measurements. Individual curves were fitted using computer software to estimate a dating adjustment factor ('k'), and a growth coefficient ('P') for each case. The predictive accuracy of the growth curves was then tested in a validation subset of the population that had a third CRL measurement. The population average curve from the developed model was also extrapolated to day 27 menstrual age (Carnegie stage 6), day 30 menstrual age (Carnegie stage 7) and day 84 menstrual age, and values were compared to previously reported measurements.

RESULTS

326 viable pregnancies were selected for CRL growth curve development. The mean time interval between CRL measurements was 20.5 days (range 2-44). The mean value for 'P' was 2.058, and for 'k' 24.6. Testing the model on a subset of 81 cases showed that the average error in predicting a third CRL measurement was 1% (SD 9.1%).

CONCLUSIONS

These new, individually fitted growth curves for the first trimester correlate more closely with the recorded embryonic lengths than other standards.

Management of women referred to an acute gynecology unit: impact of an ultrasound-based model of care

OBJECTIVE

To assess the impact of the introduction of an ultrasound-based model of care for women with acute gynecological complications.

METHODS

This was a prospective comparative study of women attending an ultrasound-based acute gynecology unit (AGU) at the Nepean Hospital during a 6-week period 4 months after the unit's inception (new model of care), and a group of women presenting at the hospital during a similar period 6 months immediately prior to the unit's inception (traditional model). In the new model of care, ultrasound was performed at the time of the initial assessment by a senior clinician. The main outcome measures were admission rates and occupied bed days.

RESULTS

The study included 290 consecutive women with complete data, 133 before and 157 after the introduction of the AGU. Compared with the group presenting before establishment of the AGU, the group who attended the AGU had significantly lower admission rate (7% vs. 36%, P < 0.0001) and significantly shorter time to see a trainee gynecologist (mean, 172 vs. 205 min, P = 0.00089), time to ultrasound examination (mean, 199 vs. 533 min, P < 0.0001), length of stay as an outpatient (mean, 45 vs. 248 min, P < 0.0001), fewer occupied bed days (total, 30 vs. 85 days, P < 0.0001) and lower surgical intervention rates (12% vs. 29%, P = 0.00025). They also had significantly higher expectant management rate (26 vs. 8%, P = 0.00023). The extrapolated annual reduction in occupied bed days represented a total financial saving of $ 257 617 Australian dollars.

CONCLUSIONS

In the AGU, the availability of ultrasound carried out by a senior clinician with an interest in gynecological emergencies may lead to a reduction in admissions and improved outcomes.

Ultrasound diagnosis of fetal macrosomia: a comparison of weight prediction models using computer simulation

OBJECTIVE

To assess the frequency of the diagnosis of macrosomia in relation to differing weight estimation formulae in unselected pregnancies.

METHODS

Computer modeling techniques were employed. Computer modeling software generated correlated fetal biometry measurements according to published British standards, from 37 to 41 weeks' gestation. For each set of measurements, estimated fetal weights were obtained by a panel of 18 ultrasound weight formulae. The diagnosis of macrosomia was made if the fetal weight estimate was greater than 4500 g. Cohorts of 5000 pregnancies for each week of gestation were studied.

RESULTS

The frequency of diagnosis of macrosomia increased progressively with advancing gestational age, with large increases between 40 and 41 weeks. The type of weight estimation formula had a profound influence on the frequency of diagnosis of macrosomia. Five of the formulae tested almost never returned a weight estimate greater than 4500 g. Three formulae yielded false positive rates in excess of 15%. The Hadlock group of formulae yielded frequencies of 0.3% to 14.6%.

CONCLUSIONS

Most formulae tend to over-diagnose macrosomia at term. Intervention rates for suspected fetal macrosomia may be influenced by gestational age at the time of scan and the type of fetal weight estimation formula in use.

Technical factors in early amniocentesis predict adverse outcome. Results of the Canadian Early (EA) versus Mid-trimester (MA) Amniocentesis Trial

The purpose of this study was to identify risk factors for fetal loss and other pregnancy complications associated with genetic amniocentesis. Data were acquired in the Canadian Early Amniocentesis Trial (CEMAT), a multicentered (12) prospective, randomized trial comparing continuous ultrasound-guided early amniocentesis (EA) and mid-trimester amniocentesis (MA) (CEMAT Group, 1998). Details of the procedure were recorded and analysed by allocation (EA versus MA), operator and centre, and correlated with pregnancy outcome. A total of 62 spontaneous pregnancy losses occurred between the procedure and 20 weeks' gestation among the 3691 patients who received their procedures within the allocated window (EA=53/1916, MA=9/1775). Technical factors correlating with these losses included procedures 'judged to be difficult' by the operator, and post-procedure amniotic fluid leakage or bleeding. Maternal risk factors included maternal hypertension (fetal loss 11. 1 per cent, compared with non-hypertensive women, 2.6 per cent) increased body mass index (BMI) and gravidity of three or greater. Allocation to EA was predictive of fetal loss, as well as failed procedure, multiple needle insertions, amniotic fluid leakage, failed culture and talipes equinovarus, in excess compared with MA. In conclusion, in this large prospective randomized trial evaluating amniocentesis, specific maternal, fetal and procedural variables were found to be predictive of fetal loss and adverse pregnancy outcome. Performing amniocentesis before 13 weeks' gestation (EA) was the major predictive factor for adverse outcome. These data suggest that first-trimester chorionic villus sampling (CVS) and MA will likely remain the invasive procedures of choice for evaluation of fetal karyotype.

Fetal tumors associated with hydrops: the role of the pediatric surgeon

Fetal tumors are being diagnosed with increasing frequency and great accuracy by antenatal ultrasound. High-output cardiac failure and hydrops indicate fetal distress. Management may be limited by the gestational age of the fetus. Our experience with three fetal tumors demonstrates the dilemma with respect to timing of delivery and prognosis. Following the diagnosis of a large sacrococcygeal tumor, a 22-week-gestation fetus became hydropic and died. Another fetus with a rapidly growing posterolateral chest wall mass required cesarean section delivery at 29 weeks gestation. Postnatal course was complicated by pulmonary hypoplasia, intratumoral hemorrhage, and death. The third fetus had an enlarging tumor in the right lobe of the liver. Poor biophysical profile and mild hydrops necessitated cesarean section delivery at 34 weeks. Right hepatic lobectomy was performed and the infant was subsequently discharged home at one month of age. The deleterious effects of the fetal tumor and the need for its removal have to be carefully weighed against the ability of the fetus to survive postnatally.

The intrauterine diagnosis of hemoglobin disorders

This article presents an overview of the use of fetal blood and DNA for prenatal testing. The molecular organization of the human hemoglobin genes, the structure of human hemoglobins, and the molecular defects of hemoglobinopathies are also discussed.