Population-based trends in prenatal screening and diagnosis for aneuploidy: a retrospective analysis of 38 years of state-wide data

OBJECTIVE

To analyse population-based trends over the entire history of prenatal testing for aneuploidy.

DESIGN

Retrospective analysis of state-wide data sets.

SETTING

Australian state of Victoria with ~70 000 annual births.

POPULATION

All pregnant women undergoing invasive prenatal testing at <25 weeks' gestation from 1976 to 2013.

METHODS

Analysis of three state-wide data sets: (1) Prenatal diagnosis data set of 119 404 amniocenteses and chorionic villus samplings from 1976 to 2013; (2) central serum screening laboratory data set from 1996 to 2013; (3) government birth statistics from 1976 to 2013.

MAIN OUTCOME MEASURES

Annual numbers and uptake rates of invasive prenatal tests and serum screening, indications for invasive prenatal testing, prenatal diagnoses of aneuploidy, diagnostic yield of invasive tests.

RESULTS

Annual numbers of invasive prenatal tests climbed steadily from 1976, then declined from 2000. In 2013, the number of invasive prenatal tests was the lowest in 25 years, while the number of trisomy 21 diagnoses was the highest ever recorded. Annual uptake of serum screening climbed from 1.6 to 83% over 1996-2013. Results from 2013 showed a high diagnostic yield (15.8%) for a low rate of invasive testing (3.4% of births). Over four decades, the number of invasive procedures performed for each diagnosis of major chromosome abnormality declined from 100 to six.

CONCLUSIONS

This study demonstrates historic reductions in the proportion of women undergoing invasive testing and dramatic improvements in diagnostic yield. Monitoring the impact of new prenatal technologies on this progress remains an important research priority.

TWEETABLE ABSTRACT

Invasive prenatal testing has reached historic lows due to dramatic improvements in Down syndrome screening.

Do women know that prenatal testing detects fetuses with Down syndrome?

This questionnaire-based study in Victoria, Australia, examined the responses of pregnant women, aged 37 years and over, to a question about what they expected prenatal testing (screening and/or diagnosis) for birth defects to tell them about their pregnancy. Content analysis showed that, of the 432 tested women, 61.3% mentioned Down syndrome, chromosomal abnormalities or trisomies. Women undergoing both screening and diagnosis were more likely than those having one or other test to mention Down syndrome (adjusted OR = 1.6, P = 0.06), having adjusted for age, marital status, education, residence and parity. Similarly, those from an English-speaking background were more likely to mention Down syndrome, etc. compared to women from a non-English-speaking background (adjusted OR = 3.5, P < 0.001). Down syndrome, a fundamental piece of information about prenatal tests, was not mentioned in nearly 40% of women's responses. This suggests that pregnant women need clearer information about prenatal testing, including the conditions that might be detected.

Follow up and evaluation of the Victorian first-trimester combined screening programme for Down syndrome and trisomy 18

OBJECTIVE

The objective of this study was to follow up and evaluate the statewide first-trimester combined screening programme for Down syndrome and trisomy 18 at Genetic Health Services Victoria, Australia.

DESIGN

Retrospective population cohort.

SETTING

Maternal Serum Screening Laboratory records.

SAMPLE

All women screened between February 2000 and June 2002 (16,153 pregnancies).

METHODS

Screening results were matched to Victorian perinatal and birth defect data via record linkage, with an ascertainment of 96.8% of pregnancy outcomes. Manual follow up with health professionals increased ascertainment to more than 99%.

MAIN OUTCOME MEASURES

Fetal Down syndrome or trisomy 18, and combined screen results, to calculate test characteristics.

RESULTS

Using a risk threshold of 1 in 300 at time of ultrasound, the sensitivities for standard first-trimester combined screening and augmented 13-week combined screening for Down syndrome were 87.3 and 90.5% and the false-positive rates (FPR) were 4.1 and 3.9%, respectively. The sensitivity for trisomy 18 was 66.7% (10/15, 95% CI 42.8-90.5%) with a 0.4% FPR and 15.2% positive predictive value (1 in 250 risk threshold).

CONCLUSIONS

The combined use of record linkage and manual follow-up techniques was effective in ascertaining more than 99% of pregnancy outcomes for calculations of accurate test characteristics of the combined screen. The sensitivity for Down syndrome at Genetic Health is comparable to similar populations. However, the sensitivity for trisomy 18 is lower than that elsewhere, which may reflect the overall low birth prevalence of trisomy 18 and associated small numbers in this particular cohort.

Population-based study of antenatal detection of congenital heart disease by ultrasound examination

OBJECTIVES

Ultrasound-based screening is widely employed for the detection of congenital malformations in utero including congenital heart disease (CHD), but there is widespread variability in the efficacy of screening programs. We aimed to evaluate current antenatal detection rates of selected congenital heart defects in Victoria.

METHODS

Data were collected from the Victorian Perinatal Data Collection Unit and Birth Defects Registry. There were 631 209 births in Victoria (1993-2002), of which 4897 cases had CHD. Cases included live births, stillbirths and termination of pregnancies because of CHD. We reviewed all cases from 1999 to 2002 with atrioventricular septal defect, simple coarctation of the aorta, double-inlet or -outlet ventricle, hypoplastic left heart syndrome, simple transposition of the great arteries (TGA), tetralogy of Fallot and truncus arteriosus. Outcome measures were antenatal diagnosis, pregnancy outcome and associated malformations.

RESULTS

The overall birth prevalence of CHD from 1993 to 2002 in Victoria was 7.8/1000. The antenatal detection rate for the seven selected defects from 1999 to 2002 was 52.8%. All but 4.8% of the cases had an ultrasound examination at > 13 weeks' gestation. Antenatal detection was highest for hypoplastic left heart syndrome (84.6%) and lowest for simple TGA (17.0%).

CONCLUSIONS

This study shows wide variation in the antenatal detection rate of CHD in Victoria. The low antenatal detection rate of TGA, a defect that should be detected easily, demonstrates suboptimal routine obstetric anomaly scanning.

Growth, behavior, and clinical findings in 27 patients with Kabuki (Niikawa-Kuroki) syndrome

This study was undertaken to document the phenotype of Kabuki (Niikawa-Kuroki) syndrome in patients from Australia and New Zealand, with particular emphasis on growth patterns, behavior, and relationship between head circumference and intellectual level. Data on 27 children and adults with Kabuki (Niikawa-Kuroki) syndrome from Australia and New Zealand were collected by questionnaire and clinical assessment. The patients ranged in age from 7 months to 36 years with a mean age of 7 years and 2 months. The mean age at diagnosis was 3(5/6) years, but in most cases, the facial phenotype was evident from infancy. The minimum birth prevalence was calculated at 1 in 86,000. Three of our patients died. Parents reported a behavior phenotype characterized by an excellent long-term memory and avoidance of eye contact. No correlation was found between head circumference and severity of intellectual disability. Eight of 14 patients over the age of 5 years were overweight or obese. Six of these eight patients had failure to thrive in infancy. One patient developed insulin-dependent diabetes mellitus in adolescence. Some individuals with Kabuki (Niikawa-Kuroki) syndrome show a characteristic growth profile with failure to thrive in infancy progressing to obesity or overweight in middle childhood or adolescence. A behavior phenotype was noted which requires further investigation. Head size is not a predictor of degree of intellectual disability.

Newborn screening for congenital hypothyroidism, Victoria, Australia, 1977-1997. Part 1: The screening programme, demography, baseline perinatal data and diagnostic classification

Clinical, demographic and laboratory data from infants with congenital hypothyroidism (CH) born in the Australian state of Victoria from the commencement of neonatal screening in mid-1977 until December 1988 are reported. These provide a baseline for a 12-year prospective longitudinal study on physical and neuro-psychological outcome until mid-1997, the subject of a second paper. Infants with CH were detected using a primary TT4 screening test. Demographic data were collected prospectively using a clinical assessment protocol. Nearly all affected infants underwent 99mTc pertechnetate scanning at the initial assessment to determine the underlying aetiology of their hypothyroidism. 704,723 infants were screened and 199 with permanent primary hypothyroidism (one in 3,541) were identified. The most common aetiologies were thyroid ectopia (46%), thyroid aplasia (33%), and 'dyshormonogenesis' (11%). The clinical abnormalities classically described in CH were more evident in infants with aplasia, and the striking female preponderance in infants with thyroid dysplasia (syn. dysgenesis) was confirmed. Other features included increased frequencies of 'dyshormonogenesis' in infants of parents of Middle-Eastern origin and of labour induction in infants with dysplasia. A closed posterior fontanelle was not found in any infant with thyroid aplasia.

Prenatal diagnosis for women aged 37 years and over: to have or not to have

Forty percent of pregnant women aged 37 years and over do not have prenatal diagnosis despite being eligible for a free test. The present study aimed to determine how often, and which, untested women were making a choice about this, how many declined an offer and why. A questionnaire was given to untested women, aged 37 years and over, at no less than 24 weeks gestation. A total of 375 (81.5%) women declined, 72 (16%) were not offered a test and 13 presented too late antenatally. There was a three-fold increased likelihood (OR 3.10 95% CI 1.44, 6.65) of no offer for urban non-English speaking background women, compared with the reference group (metropolitan, English speaking). Unpartnered women were also significantly less likely to receive an offer (OR 3.18, 95% CI 1.19, 8.46). Risk to the baby was the main reason for declining. When offered non-invasive prenatal screening, most decliners of prenatal diagnosis accepted, even those who declined because they were opposed to abortion. We estimate that overall 33% of older pregnant women were being offered and declining amniocentesis and/or chorion villus sampling (CVS). Only 6% were not offered a test, but this small proportion is over-represented by minority groups who must be given equal opportunity to make this choice.

Neural tube defects in Victoria, Australia: potential contributing factors and public health implications

OBJECTIVES

To measure population prevalence and determine potential predictors of neural tube defects.

METHOD

Analysis of all births reported to a mandated collection of perinatal data, and terminations prior to 20 weeks' gestation that have been reported to a data collection of birth defects in Victoria from 1983 to 1997. Prevalence at birth and risk ratios of infant and maternal characteristics associated with neural tube defects were calculated.

RESULTS

Prevalence of spina bifida has remained steady for 15 years and was 8.8/10,000 in 1997. Anencephaly increased to 7.9/10,000 in 1997. After exclusion of pregnancy terminations, the 1997 birth prevalence was 4.5/10,000 for spina bifida and 2.4/10,000 for anencephaly. Neural tube defects are identified in 1 in 1600 fetuses, the risk being significantly higher for epileptic women (Adjusted Odds Ratio (AOR) = 3.70, 95% CI 2.25-6.07), multiple births (AOR = 4.56, 95% CI 3.46-6.02), teenage mothers (AOR = 1.47, 95% CI 1.09-2.00) compared with those aged 25-29, and women with three or more previous pregnancies (AOR = 1.40, 95% CI 1.10-1.78). The risk was lower for women of East Asian (AOR = 0.70, 95% CI 0.49-1.00) and Middle Eastern origin (AOR = 0.60, 95% CI 0.35-1.02) and these differences were approaching statistical significance.

CONCLUSION

Total prevalence of neural tube defects did not decline up to 1997.

IMPLICATIONS

It is unlikely that targeting 'at risk' groups identified in this study would make a difference to neural tube defect incidence. However, consideration could be given to identifying larger 'at risk' groups such as those with homocysteine metabolism defects.

Evidence that severe asthma can be divided pathologically into two inflammatory subtypes with distinct physiologic and clinical characteristics

The mechanisms associated with the development of severe, corticosteroid (CS)-dependent asthma are poorly understood, but likely heterogenous. It was hypothesized that severe asthma could be divided pathologically into two inflammatory groups based on the presence or absence of eosinophils, and that the inflammatory subtype would be associated with distinct structural, physiologic, and clinical characteristics. Thirty-four severe, refractory CS-dependent asthmatics were evaluated with endobronchial biopsy, pulmonary function, allergy testing, and clinical history. Milder asthmatic and normal control subjects were also evaluated. Tissue cell types and subbasement membrane (SBM) thickness were evaluated immunohistochemically. Fourteen severe asthmatics [eosinophil (-)] had nearly absent eosinophils (< 2 SD from the normal mean). The remaining 20 severe asthmatics were categorized as eosinophil (+). Eosinophil (+) severe asthmatics had associated increases (p < 0.05) in lymphocytes (CD3+, CD4+, CD8+), mast cells, and macrophages. Neutrophils were increased in severe asthmatics and not different between the groups. The SBM was significantly thicker in eosinophil (+) severe asthmatics than eosinophil (-) severe asthmatics and correlated with eosinophil numbers (r = 0.50). Despite the absence of eosinophils and the thinner SBM, the FEV(1) was marginally lower in eosinophil (-) asthmatics (p = 0.05) with no difference in bronchodilator response. The eosinophil (+) group (with a thicker SBM) had more intubations than the eosinophil (-) group (p = 0.0004). Interestingly, this group also had a decreased FVC/slow vital capacity (SVC). These results suggest that two distinct pathologic, physiologic, and clinical subtypes of severe asthma exist, with implications for further research and treatment.

Collagen deposition in large airways may not differentiate severe asthma from milder forms of the disease

Chronic airway inflammation and remodeling, including fibrosis, have been proposed as important contributors to asthma pathophysiology. Previous studies of airway fibrosis have been performed mainly in mild and moderate asthmatics at the subepithelial "basement membrane" (SBM) level. The current study was designed to evaluate the large airway SBM thickness and submucosal collagen deposition, as measured by three different collagen staining methods, in endobronchial biopsies from 17 severe, nine moderate, and seven mild asthmatics, as well as eight normal control subjects. Tissue eosinophils and transforming growth factor-beta (TGF-beta) immunoreactivity were also examined. There were no statistically significant differences in the SBM thickness, submucosal collagen deposition, eosinophil numbers, or TGF-beta positive cells among the three groups of asthmatics and the normal control subjects. It was only when examining all asthmatics (n = 33) together, that a modestly thickened SBM (p = 0.04), as evaluated by collagen type III immunostaining, was observed as compared with normal control subjects. Despite this difference, no significant differences were found in the amount of submucosal collagen deposition and the number of eosinophils or TGF-beta expressing cells when comparing total asthmatics and normal control subjects. Additionally, no significant correlations were found between collagen deposition and eosinophil count, TGF-beta expression level, FEV1, or duration of asthma. These results suggest that although increased collagen deposition in the SBM at the large airway level is a characteristic of asthma, it may not explain the differences in severity of asthma.

Associations between congenital malformations and childhood cancer. A register-based case-control study

This report describes a population-based case-control study that aimed to assess and quantify the risk of children with congenital malformations developing cancer. Three sources of data were used: the Victorian Cancer Register, the Victorian Perinatal Data Register (VPDR) and the Victorian Congenital Malformations/Birth Defects Register. Cases included all Victorian children born between 1984 and 1993 who developed cancer. Four controls per case, matched on birth date, were randomly selected from the VPDR. Record linkage between registers provided malformation data. A matched case-control analysis was undertaken. Of the 632 cancer cases, 570 (90.2%) were linked to the VPDR. The congenital malformation prevalence in children with cancer was 9.6% compared with 2.5% in the controls [odds ratio (OR) 4.5, 95% CI 3.1-6.7]. A strong association was found with chromosomal defects (OR=16.7, 95% CI 6.1-45.3), in particular Down's syndrome (OR=27.1, 95% CI 6.0-122). Most other birth defect groups were also associated with increased cancer risk. The increased risk of leukaemia in children with Down's syndrome was confirmed, and children with central nervous system (CNS) defects were found to be at increased risk of CNS tumours. The report confirms that children with congenital malformations have increased risks of various malignancies. These findings may provide clues to the underlying aetiology of childhood cancer, as congenital malformations are felt to be a marker of exposures or processes which may increase cancer risk. The usefulness of record linkage between accurate population-based registers in the epidemiological study of disease has also been reinforced.

Fetal outcome and maternal morbidity after early amniocentesis

We have studied a large population-based cohort of women who had amniocentesis at 14 weeks' gestation (early amniocentesis) in Victoria, a state of Australia, to determine fetal loss rates and maternal morbidity. This was done by linking two registers--one containing information on all prenatal diagnostic tests in the state, and the other a register of all births at or after 20 weeks' gestation. Almost complete follow-up was achieved. The spontaneous fetal loss rate was significantly higher for women of age 37 years and over having early amniocentesis (2.5 per cent), as compared with the fetal loss rate found previously on the same geographically defined population who had amniocentesis at about 16 weeks' gestational age (1.1 per cent). Three classes of maternal morbidity reported to the birth register (post 20 weeks' gestation) were also analysed. The most significant finding was a reduced rate of premature rupture of membranes with early amniocentesis when compared with a group having later amniocentesis, or the background population not having any amniocentesis. There was no significant increase in the occurrence of antepartum bleeding or genito-urinary tract infection for women having early amniocentesis. These data agree with other studies in showing that early amniocentesis is associated with a significant increased risk of fetal loss, as compared with later amniocentesis. In addition we have shown no significant increase in the occurrence of three indicators of maternal morbidity, reported at or after 20 weeks' gestation.

Congenital malformations in Victoria, Australia, 1983-95: an overview of infant characteristics

OBJECTIVE

To provide an overview of the characteristics of Victorian infants born between 1983 and 1995 who are affected by one or more of 27 sentinel birth defects.

METHODOLOGY

Using data on congenital malformations supplied to the Victorian Perinatal Data Collection Unit from multiple sources between 1983 and 1995, information was summarised for 25231 infants (born at 20 weeks or more) and 1566 terminations of pregnancy before 20 weeks' gestation.

RESULTS

During the 13-year study period in Victoria, 3.2% of babies had at least one malformation. Congenital dislocation of the hip was the most common defect with a prevalence of 28.9 per 10000 pregnancies or 1/346. Increase in birth prevalence between 1983 and 1995 is greatest in obstructive defects of the renal pelvis, hypospadias and the trisomies 21,13 and 18. Nearly 50% of pregnancies affected by anencephaly were terminated before 20 weeks compared to 26% affected by spina bifida. The perinatal mortality of infants born at 20 weeks or more with congenital malformations is more than 10 times greater than that of infants without any malformations. Males are more at risk of being born with a malformation than females. Congenital malformations are more common in infants of multiple pregnancies and those of low birthweight.

CONCLUSION

This large data collection is a valuable source of information for perinatal epidemiologists, for providers of prenatal diagnostic services and for the care of the disabled. In addition, the continued reporting and monitoring of birth defects will allow for targeted research that may lead to a better understanding of their aetiology.

Prenatal exposure to phenytoin, facial development, and a possible role for vitamin K

Ten patients with maxillonasal hypoplasia (Binder "syndrome"), who were prenatally exposed to phenytoin (usually in combination with other anticonvulsants), were identified retrospectively. In addition to their facial anomalies, 6 of the patients were radiographed neonatally and showed punctate calcification, characteristic of chondrodysplasia punctata. Evidence is presented that the facial abnormalities seen in these children are due to anticonvulsant-induced vitamin K deficiency, causing abnormal development of the cartilaginous nasal septum. We propose that early vitamin K supplementation of at-risk pregnancies may prevent the development of maxillonasal hypoplasia, which in some patients is severely disfiguring and causes great emotional distress. Correction of this facial defect requires surgical and dental treatment over a long period of time.

New estimates of Down syndrome risks at chorionic villus sampling, amniocentesis, and livebirth in women of advanced maternal age from a uniquely defined population

Current measures of livebirth prevalence of Down syndrome are derived from data obtained up to 20 years ago, before the introduction of the prenatal diagnostic tests amniocentesis and chorionic villus sampling (CVS). For women aged 36-52 years, but who were not tested prenatally, we proposed to make a direct estimate of current livebirth prevalence of Down syndrome. We could also determine prevalence at the time of CVS and amniocentesis in women of the same age undergoing prenatal testing. Differences in these prevalences allow an estimation of the relative loss of Down syndrome during pregnancy. In Victoria, Australia, we identified 3041 women having CVS, 7504 having amniocentesis, and 13,139 having no test. Smoothed regression estimates of age-specific livebirth prevalence were found to be higher than in the early studies. The estimate of spontaneous loss was 17 per cent between the time of CVS and amniocentesis, and 18 per cent after the time of amniocentesis. The latter figure is lower than previous estimates and may be explained by a greater likelihood of a Down syndrome fetus surviving to be liveborn, given the modern approach to early obstetric intervention. These current risk estimates of livebirth may be useful updates for genetic counselling, but perhaps more importantly, may be used as precise maternal age-related risk figures, necessary in the design and implementation of prenatal screening programmes for Down syndrome.

Binder's syndrome due to prenatal vitamin K deficiency: a theory of pathogenesis

There is evidence that vitamin K-deficiency during human pregnancy can be caused by the therapeutic use of warfarin or phenytoin. The pregnancy histories of three cases of Binder's syndrome are reported. One was associated with warfarin exposure, one with phenytoin exposure and one with alcohol abuse. It is proposed that Binder's syndrome can be caused by prenatal exposure to agents that cause vitamin K-deficiency. Sprague-Dawley rats were treated from postnatal day 1 to 12 weeks with daily doses of warfarin (100 mg/kg) and concurrent vitamin K1 (10 mg/kg). This regimen creates a net extra-hepatic vitamin K-deficiency. The treated rats developed with a distinct facial appearance characterized by a markedly reduced snout. Histological examination showed that the normally non-calcified septal cartilage was extensively calcified. It is proposed that normal growth of the septal cartilage is necessary for the development of the profile of the nose and midface and that normal growth will only take place while the septal cartilage is uncalcified.

Importance of complete follow-up of spontaneous fetal loss after amniocentesis and chorion villus sampling

Women who are the most difficult to trace after amniocentesis or chorion villus sampling are often those who have had an adverse pregnancy outcome. To calculate total fetal loss figures for use in prenatal counselling we have followed in a multicentre study 100% of women who had undergone these procedures. Early spontaneous loss (within three weeks of the procedure) and total spontaneous loss were much lower after amniocentesis (0.2% and 1.3%, respectively) than after chorion villus sampling (1.2% and 2.9%). Four spontaneous fetal losses among the 20 pregnancies that were the most difficult to follow-up increased the loss rate by 0.5% for chorion villus sampling. Risk of early fetal loss after chorion villus sampling was related to experience of the operator (relative risk [RR] 4.3, p = 0.003), and total fetal loss was lower in pregnancies tested at 10 weeks' or more gestational age compared with those tested before 10 weeks' (RR 0.4, p = 0.01). A table showing the frequency of each of the seven possible outcomes after amniocentesis and chorion villus sampling is useful in counselling those considering one or other test.

Transabdominal chorion villus sampling: a safe and reliable procedure

A complete follow-up of the first 578 patients undergoing transabdominal chorion villus sampling (TACVS) in our combined practices was undertaken to determine the pregnancy loss rate. Factors contributing to losses and the problems incurred in achieving a clinically relevant result were also examined. It was found that increasing experience led to fewer procedural difficulties but that there persisted a higher problem rate in those women with a retroverted uterus. In 98.1% of patients an adequate volume of tissue was obtained and in 95.5% a clinically relevant result was achieved. This second figure rose to 96.3% in the latter part of the study. There was a total fetal loss rate of 2%, with only 0.5% (3 patients) having a missed abortion within 4 weeks of the procedure. It is concluded that TACVS is a reliable procedure with a high level of safety.

Congenital absence of pyramids and its significance in genetic diseases

Bilateral absence of the pyramids, best assessed in transverse sections of the medulla oblongata, was found in 0.7% of 2,850 autopsies performed at the Royal Children's Hospital, Melbourne (Australia). A strong association with some forms of congenital aqueductal stenosis was observed and evaluated in further cases ascertained through other hospitals. The very strong association observed with X-linked congenital aqueduct stenosis may be useful diagnostically but must be evaluated in other centres. At least, the presence of pyramids seems strong evidence against this diagnosis. Absence of the pyramids was also observed in several known or new genetic syndromes - Meckel's syndrome, the HARD syndrome, two sisters with congenital aqueductal stenosis and polydactyly and two families with microcephaly and arthrogryposis.

Fragile (X)(q27) sites in a pedigree with female carriers showing mild to severe mental retardation

A pedigree showing the fragile site at Xq27 in a severely retarded female and in other less retarded carriers is described. Two of the four moderately retarded males with the fra(X)(q27) show macro-orchidism, and a variety of other features usually used to support the effects of the fra(X)(q27) are also inconsistent. A second fragile site at (10)(q23) is also present and in the two oldest females its frequency is not decreased, whereas the fra(x)(q27) is not detectable in these females although probably present. It is concluded that pedigrees showing mentally retarded females and probable X linkage should be included in studies of the fra(X)(q27).

The Psychological Approach to Rheumatism: (Section of Physical Medicine)

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