Change in prevalence of preterm birth in Israel following publication of national guidelines recommending routine sonographic cervical-length measurement at 19-25 weeks' gestation

OBJECTIVE

To compare the prevalence of preterm birth (PTB) (delivery before 37 weeks) in Israel before and after publication of national guidelines recommending second-trimester sonographic cervical-length (CL) measurement.

METHODS

The Israeli Society of Obstetrics and Gynecology (ISOG) guidelines, issued on 1 January 2012, specified that CL should be measured transabdominally or, if this is not possible, transvaginally, at the 19-25-week ultrasound anomaly scan and that CL < 25 mm should indicate further work-up and treatment, although the type of treatment was unspecified. In 2000, the Israel Ministry of Health issued a legal requirement for the submission of delivery records to a national registry. These data were used to compare PTB prevalence in the period before (2000-2011) and that after (2012-2020) publication of the guidelines, as well as trends within each time period. Information was available on singleton and multiple pregnancy and maternal age and parity, as well as low birth weight (< 2500 g).

RESULTS

During the period 2000-2020, there were 3 403 976 infants liveborn in Israel: 1 797 657 before and 1 606 319 after publication of the ISOG guidelines. There were 247 187 PTBs overall, with a prevalence of 7.64% (95% CI, 7.52-7.77%) before publication of the guidelines and 6.84% (95% CI, 6.43-7.24%) afterwards (P < 0.0002, two-tailed). The annual PTB prevalence was static in the first time period but declined by 0.18% per annum during the second period, after publication of the guidelines. The proportionate reduction in PTB prevalence after compared with before publication of the guidelines was 10% overall, 9% for PTB at 33-36 weeks, 18% for PTB at 28-32 weeks and 24% for PTB at < 28 weeks. After publication of the guidelines, reduced prevalence of PTB was observed among singletons (5.49% before vs 4.83% after, P < 0.0001), but not among infants in twin or higher-order multiple pregnancy. There was a statistically significant reduction in the rate of PTB following publication of the guidelines in both nulliparous and parous women and in the 19-39-year-old maternal-age group. Although reductions in PTB prevalence were also noted in high-risk age groups (maternal age < 19 years and ≥ 40 years), these did not reach statistical significance. Following publication of the guidelines, there was a statistically significant reduction in the prevalence of birth weight under 2500 g, of a magnitude similar to that for PTB prevalence.

CONCLUSIONS

The publication of national guidelines recommending routine CL measurement at the time of the second-trimester anomaly scan was associated with a fall in PTB prevalence in singleton pregnancies. Whilst direct evidence linking screening with this fall in prevalence is lacking, it is likely that implementation of routine CL screening played an important role in the reduction of PTB rate. Our experience indicates that screening can be incorporated into the second-trimester anomaly scan. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Quality assessment of first-trimester screening for preterm pre-eclampsia

OBJECTIVE

To assess the performance and impact of first-trimester preterm pre-eclampsia screening in a single center.

METHODS

This was a single-center study of women with a singleton pregnancy who were screened prospectively for preterm pre-eclampsia (i.e. delivery before 37 weeks' gestation) using maternal characteristics, mean arterial pressure (MAP), uterine artery Doppler pulsatility index, maternal serum pregnancy-associated plasma protein-A and placental growth factor. The individual risk for preterm pre-eclampsia was estimated from a published model, and those with a risk above 1 in 200 were recommended to take 150 mg soluble aspirin per day until 34 weeks. Information on the incidence of pre-eclampsia was obtained from the hospital register of adverse pregnancy outcomes. Screening performance indicators, including detection and false-positive rates, were estimated from the distribution of risks. Screening impact was estimated by dividing the observed prevalence by the expected prevalence, which was derived from the distribution of risks.

RESULTS

The distributions of MAP, uterine artery Doppler pulsatility index and serum markers were consistent with the risk model parameters. The estimated detection and false-positive rates were 79.7% and 16.2%, respectively. There were six cases of preterm pre-eclampsia, four of which occurred in women with a positive screening result. The prevalence was 62% of that expected, but the 95% CI of 23-140% indicated that the study was underpowered to assess the impact.

CONCLUSIONS

This study demonstrates that the performance of preterm pre-eclampsia screening can be estimated in a single center with fewer than 2000 women screened. However, in order to assess the impact of screening on the prevalence of the condition, a much larger cohort is needed. © 2022 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.

Early pregnancy prediction of spontaneous preterm birth before 32 completed weeks of pregnancy using plasma RNA: transcriptome discovery and initial validation of an RNA panel of markers

OBJECTIVE

To compare the second-trimester plasma cell-free (PCF) transcriptome of women who delivered at term with that of women with spontaneous preterm birth (sPTB) at or before 32 weeks of gestation and identify/validate PCF RNA markers present by 16 weeks of gestation.

DESIGN

Prospective case-control study.

SETTING

Academic tertiary care centre.

POPULATION

Pregnant women with known outcomes prospectively sampled.

METHODS

PCF RNAs extracted from women at 22-24 weeks of gestation (five sPTB up to 32 weeks and five at term) were hybridised to gene expression arrays. Differentially regulated RNAs for sPTB up to 32 weeks were initially selected based on P value compared with control (P < 0.01) and fold change (≥1.5×). Potential markers were then reordered by narrowness of distribution. Final marker selection was made by searching the Metacore™ database to determine whether the PCF RNAs interacted with a reported set of myometrial Preterm Initiator genes. RNAs were confirmed by quantitative reverse transcription polymerase chain reaction and tested in a second group of 40 women: 20 with sPTB up to 32 weeks (mean gestation 26.5 weeks, standard deviation ±2.6 weeks), 20 with spontaneous term delivery (40.1 ± 0.9 weeks) sampled at 16-19+5  weeks of gestation.

MAIN OUTCOME MEASURE

Identification of PCF RNAs predictive of sPTB up to 32 weeks.

RESULTS

Two hundred and ninety-seven PCR RNAs were differentially expressed in sPTB up to 32 weeks of gestation. Further selection retained 99 RNAs (86 mRNAs and 13 microRNAs) and five of these interacted in silica with seven Preterm Initiator genes. Four of five RNAs were confirmed and tested on the validation group. The expression of each confirmed PCF RNA was significantly higher in sPTB up to 32 weeks of gestation. In vitro study of the four mRNAs revealed higher expression in placentas of women with sPTB up to 32 weeks and the potential to interfere with myometrial quiescence.

CONCLUSIONS

The PCF RNA markers are highly associated with sPTB up to 32 weeks by 16 weeks of gestation.

TWEETABLE ABSTRACT

Women destined for spontaneous preterm birth can be identified by 16 weeks of gestation with a panel of maternal plasma RNAs.

First- and second-trimester maternal serum markers of pre-eclampsia in twin pregnancy

OBJECTIVE

To evaluate the distribution of first- and second-trimester maternal serum markers in twin pregnancy with and without pre-eclampsia.

METHODS

One-hundred and forty-four twin and 109 unaffected singleton pregnancies were recruited from the same institution. First- and second-trimester maternal blood samples were stored and measured retrospectively for serum placental growth factor (PlGF), pregnancy-associated plasma protein-A (PAPP-A), free β-human chorionic gonadotropin (β-hCG) and α-fetoprotein (AFP). All had measurement of first-trimester serum markers, and 167 (66%) had second-trimester tests. Values were expressed in multiples of the gestation-specific median (MoMs) in singletons, adjusted for maternal weight, as appropriate.

RESULTS

Pre-eclampsia was diagnosed in 12 (9.0%) twin pregnancies of 133 continuing beyond 22 weeks. In unaffected twin pregnancies, all serum markers were statistically significantly increased (P < 0.0001), consistent with a doubling of concentration. Among twin pregnancies, those with pre-eclampsia had a significantly reduced median PlGF compared with surviving unaffected twin pregnancies (0.96 MoM vs 1.46 MoM; P < 0.0002, two-tailed), whilst median PAPP-A, which is known to be reduced in affected singleton pregnancies, was increased (3.91 MoM vs 2.43 MoM; P < 0.0005, two-tailed). The levels of free β-hCG (P < 0.02) and AFP (P < 0.05) were also significantly raised, but to a lesser extent than was the level of PAPP-A. Using a logistic regression algorithm based on first- and second-trimester PlGF and PAPP-A, together with previously published uterine artery Doppler and mean arterial pressure measurements in the same series, the predicted pre-eclampsia detection rate was 65% for a 10% false-positive rate.

CONCLUSIONS

In twin pregnancy, the predicted detection rate of pre-eclampsia using first- and second-trimester maternal serum and biophysical markers is good. In contrast to singleton pregnancy, PAPP-A levels are raised in the first trimester of twin pregnancies destined to develop pre-eclampsia and therefore a different prediction algorithm is needed. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

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.

Nuchal translucency in twins according to mode of assisted conception and chorionicity

OBJECTIVES

The impact of nuchal translucency (NT) screening in twins conceived after use of assisted reproduction technology (ART) has not been addressed properly in the literature. The aim of the current study was to assess, in a large cohort from a single center, NT in twins following various modes of ART as compared with NT in spontaneously-conceived twins and to differentiate results with regard to chorionicity.

METHODS

Retrospective data from 825 twin pregnancies were available for this study. All pregnant women underwent NT screening and chorionicity determination between 11 + 0 and 13 + 6 weeks' gestation in our center. Information about mode of conception and pregnancy outcome was obtained from hospital records and by telephone interviews. Twins were classified as having been conceived after in-vitro fertilization (IVF) with the woman's own or a donated embryo, after non-IVF ART or spontaneously. NT distribution in subgroups of fetuses was compared on the basis of the multiple of the normal median (MoM), SD of log10 MoM estimated by the 90(th) -10(th) centile range divided by 2.563 and the proportion of NT values exceeding the normal 95(th) centile which was 1.641 MoM in the singletons.

RESULTS

NT values were statistically significantly higher in ART pregnancies as compared with spontaneously-conceived pregnancies (Wilcoxon rank-sum test, P < 0.05) with medians of 1.073 and 1.038 MoM, respectively, but the proportion with values above the normal 95(th) percentile did not differ (chi-square test, P = 0.89). Among the ART twins, NT values were significantly higher for those conceived using IVF methods (P < 0.005), with a median of 1.082 MoM, compared with a median of 1.022 MoM using other methods. However, although a greater proportion exceeded the 95(th) centile (7.3% compared with 4.8%) this difference did not reach statistical significance (P = 0.17). There were no differences in NT values according to chorionicity (Wilcoxon rank-sum test, P = 0.75). The standard deviation of log10 NT was similar for all subgroups of twins. The correlation coefficient between fetuses in ART pregnancies was statistically significantly lower than that in spontaneously-conceived pregnancies (P < 0.05) but no significant differences were found between types of ART or according to chorionicity.

CONCLUSIONS

There was a small but significant increase in NT levels among ART pregnancies, which appeared to be confined to those conceived using IVF, and a small reduction in the correlation between fetuses. These effects probably have little impact on the estimated risk based on algorithms in use today.

Non-invasive prenatal testing for aneuploidy: current status and future prospects

Non-invasive prenatal testing (NIPT) for aneuploidy using cell-free DNA in maternal plasma is revolutionizing prenatal screening and diagnosis. We review NIPT in the context of established screening and invasive technologies, the range of cytogenetic abnormalities detectable, cost, counseling and ethical issues. Current NIPT approaches involve whole-genome sequencing, targeted sequencing and assessment of single nucleotide polymorphism (SNP) differences between mother and fetus. Clinical trials have demonstrated the efficacy of NIPT for Down and Edwards syndromes, and possibly Patau syndrome, in high-risk women. Universal NIPT is not cost-effective, but using NIPT contingently in women found at moderate or high risk by conventional screening is cost-effective. Positive NIPT results must be confirmed using invasive techniques. Established screening, fetal ultrasound and invasive procedures with microarray testing allow the detection of a broad range of additional abnormalities not yet detectable by NIPT. NIPT approaches that take advantage of SNP information potentially allow the identification of parent of origin for imbalances, triploidy, uniparental disomy and consanguinity, and separate evaluation of dizygotic twins. Fetal fraction enrichment, improved sequencing and selected analysis of the most informative sequences should result in tests for additional chromosomal abnormalities. Providing adequate prenatal counseling poses a substantial challenge given the broad range of prenatal testing options now available.

First-trimester detection of major cardiac defects with the use of ductus venosus blood flow

OBJECTIVE

To assess the best method of combining fetal nuchal translucency (NT) and ductus venosus (DV) blood flow measurements in the detection of major cardiac defects in chromosomally normal fetuses during the first-trimester scan.

METHODS

During an 8-year period NT and DV blood flow were routinely assessed at 11-14 weeks' gestation. Only chromosomally normal singleton pregnancies were included in the study. When a cardiac defect was suspected, or when increased fetal NT and/or absent or reversed (AR) A-wave in the DV was observed, early fetal echocardiography was offered. Data on routine second- and third-trimester scans, neonatal follow-up or postmortem examination were obtained from hospital records. The detection and false-positive rates for all major cardiac defects were calculated for several screening strategies, including: NT or DV pulsatility index for veins (DV-PIV) above a fixed normal centile; AR A-wave; risk based on NT and DV-PIV or A-wave velocity above a fixed normal centile; and combinations of these strategies.

RESULTS

The study population included 37 chromosomally normal fetuses with a major cardiac defect and 12 799 unaffected pregnancies. Fetal NT above the 95(th) or the 99(th) centile and AR A-wave was observed in 40, 27 and 39% of the fetuses with major cardiac defects, respectively. A 47% detection rate with a 2.7% false-positive rate was obtained when AR A-wave or NT above the 99(th) centile was used as the selection criterion.

CONCLUSIONS

Half of major fetal cardiac defects could be detected in the first trimester if NT and DV Doppler are used to select 2.7% of the general pregnant population for extended fetal echocardiography.

ADAM12s as a first-trimester screening marker of trisomy

OBJECTIVE

To evaluate the potential of maternal serum A Disintegrin And Metalloprotease 12-S (ADAM12s) as an additional marker for the combined test in the Dutch first-trimester national Down syndrome (DS) screening program.

METHODS

Serum samples were collected between 2004 and 2007 as part of the national program. A total of 218 singleton cases of trisomy 21 (DS), 62 trisomy 18 (Edwards syndrome) and 29 trisomy 13 (Patau syndrome) were identified. All cases were matched with controls for gestation, maternal weight and maternal age. The serum concentration of ADAM12s was determined 'blind' to outcome and expressed in multiples of the gestation-specific median for controls (MoM).

RESULTS

The median ADAM12s was 1.00 MoM in controls and in the DS cases at 8, 9, 10, 11, 12, 13 weeks it was 0.45 (n = 3), 0.73 (22), 0.74 (53), 0.85 (37), 0.92 (71), 1.06 (32) MoM, respectively. The median for trisomy 18 was 0.85 MoM and for trisomy 13 0.63 MoM.

CONCLUSION

The ADAM12s MoM values were clearly reduced in early first-trimester for all trisomies. However, the screening performance for DS did not greatly improve adding ADAM12s. ADAM12s could be an additional biochemical marker for first-trimester screening for trisomies other than DS.

Bedside estimation of Down syndrome risk from second-trimester ultrasound prenasal thickness

OBJECTIVES

To construct tables for 'bedside' estimation of Down syndrome risk based on maternal age and ultrasound prenasal thickness (PT) measurements.

METHODS

Likelihood ratios were calculated using a log Gaussian model of the PT distribution in multiples of the gestational age-specific median (MoM). The model parameters were derived from 80 Down syndrome and 850 unaffected pregnancies scanned at 14-27 weeks; these data had been published previously, in three series, except for 18 Down syndrome and 119 affected pregnancies. The means were estimated as the median, and the SDs as the 10(th)-90(th) range divided by 2.563.

RESULTS

A log Gaussian model fitted well the distribution of PT values in Down syndrome and unaffected pregnancies with medians of 1.31 MoM and 1.01 MoM, and log(10) SDs of 0.075 and 0.082, respectively.

CONCLUSIONS

The tables provide a simple 'bedside' estimation of Down syndrome risk without the need for computerized software or complicated calculations. More prospective data on PT in combination with other first- and second-trimester screening markers are needed.

Correlation between nuchal translucency and nuchal skin-fold measurements in Down syndrome and unaffected fetuses

OBJECTIVE

To assess whether there is a correlation between nuchal translucency (NT) and nuchal skin-fold (NF) measurements, in Down syndrome and in normal pregnancies.

METHODS

Nineteen Down syndrome and 224 normal fetuses underwent ultrasound sequential examinations at 11-13 weeks and 14-28 weeks' gestation. NT was measured at the earlier examination and NF at the later one. Both markers were expressed in multiples of the normal gestation-specific median (MoM). The affected cases had been referred to us for termination of pregnancy; NT had been measured locally and NF was measured at our center prior to the procedure. All unaffected pregnancies were scanned routinely at our center.

RESULTS

There was no statistically significant correlation between NT and NF, in either the Down syndrome (r = 0.076, P = 0.76) or the unaffected (r = - 0.021, P = 0.76) pregnancies. The median NF value in Down syndrome fetuses was 1.538 MoM, compared with 0.990 in unaffected fetuses (P < 0.0001). Gaussian modeling with parameters from a published meta-analysis, updated to include the current series, predicted a 91% detection rate of Down syndrome for a 5% false-positive rate when NF replaced second-trimester biochemistry in a sequential contingent screening strategy.

CONCLUSION

While this study cannot exclude a small correlation between NT and NF, and the Down syndrome karyotype was known at the time of the NF scan, the markers can be considered as independent determinants of Down syndrome risk. Modeling suggests that sequential contingent screening incorporating NF is an effective screening strategy, although this needs to be confirmed in a prospective study.

Combining fetal nuchal fold thickness with second-trimester biochemistry to screen for trisomy 21

OBJECTIVE

To assess second-trimester screening for trisomy 21 by combining ultrasound nuchal fold (NF) measurement with maternal serum biochemistry.

METHODS

NF, maternal serum alpha-fetoprotein (AFP) and free beta-human chorionic gonadotropin (beta-hCG) were determined concurrently at 14-19 weeks' gestation in a study population comprising 1813 women with singleton pregnancies, including 1257 unselected women undergoing serum screening for trisomy 21 (1999-2002), and 556 high-risk pregnancies prior to amniocentesis (2003-2005), 402 of whom had positive serum screening tests. The results were expressed in multiples of the gestation-specific normal median (MoMs).

RESULTS

There were 1799 unaffected singleton pregnancies, and their NF values approximately fitted a log Gaussian distribution over a wide range. There was a weak but statistically significant correlation between log NF and log AFP (r = - 0.069, P < 0.005) and the correlation coefficient between log NF and log free beta-hCG was even smaller and not statistically significant (r = 0.038, P = 0.11). Among the seven trisomy 21 pregnancies, the median NF level was 1.53 MoM (geometric mean 1.75 MoM), a highly statistically significant increase compared with unaffected pregnancies (P < 0.0001, one-tail Wilcoxon Rank Sum Test). In pregnancies referred because of positive serum screening tests (391 unaffected, seven cases of trisomy 21, one of monosomy X and three other chromosomal anomalies) the use of NF to modify the serum screening risk would have reduced the invasive procedures in unaffected pregnancies by 46% without affecting the detection rate of trisomy 21 or other anomalies. Statistical modeling predicted that adding NF to AFP and free beta-hCG would increase detection more than would adding unconjugated estriol as well as inhibin-A, an analyte that is difficult to measure with precision.

CONCLUSIONS

The addition of NF measurement to second-trimester biochemical markers improves screening performance, and could overcome drawbacks in the implementation of inhibin-A assay in clinical practice.

Dépistage de la trisomie 21 par le test combiné du premier trimestre suivi par l'échographie du second trimestre en population générale

BACKGROUND

Recent studies have reported the efficacy of first trimester combined screening for Down Syndrome based on maternal age, serum markers (human chorionic gonadotropin, pregnancy-associated plasma protein A), and ultrasound measurement of fetal nuchal translucency. However, those do not incorporate the value of the widely accepted routine 20-22 week anomaly scan.

STUDY DESIGN

We carried out a multi-centre, interventional study in the unselected population of a single health authority in order to assess the performance of first trimester combined screening, followed by routine second trimester ultrasound examination and/or screening by maternal serum markers (free beta-hCG and alpha-fetoprotein measurement or total hCG, alpha-fetoprotein and unconjugated estriol measurement) when incidentally performed. Detection and screen positive rates were estimated using a correction method for non verified issues. A cost analysis was also performed.

RESULTS

During the study period, 14,934 women were included. Fifty-one cases of Down Syndrome were observed, giving a prevalence of 3.4 per 1000 pregnancies. Of these, 46 were diagnosed through first (N=41) or second (N=5) trimester screening. Among the 5 screen-negative Down syndrome cases, all were diagnosed postnatally after an uneventful pregnancy. Detection and screen positive rates of first trimester combined screening were 79.6% and 2.7%, respectively. These features reached 89.7 and 4.2%, respectively when combined with second trimester ultrasound screening. The average cost of the full screening procedure was 108 euro (120 $) per woman and the cost per diagnosed Down syndrome pregnancy was 7,118 euro (7,909 $).

CONCLUSION

Our findings suggest that one pragmatic interventional two-step approach using first-trimester combined screening followed by second trimester detailed ultrasound examination is a suitable and acceptable option for Down syndrome screening in pregnancy.

A model for second-trimester Down syndrome sonographic screening based on facial landmarks and digit length measurement

OBJECTIVE

To determine whether Down syndrome can be detected by combining measurements of fetal nasal bone (NB) length, prenasal thickness (PT) and digits 2 and 3 of the hand.

METHODS

Two hundred and fifty-four normal and 25 Down-syndrome fetuses were scanned between 15 and 33 weeks' gestation. Physicians performing the scans were not blinded to the fetal karyotype. Both PT and NB were measured in a mid-sagittal plane. For PT measurement calipers were placed between the frontonasal angle and the outer skin edge. Digits 2 and 3 of one hand were also measured. The results (except for PT/NB ratio) were expressed in multiples of the normal gestation-specific median (MoM). A logistic regression model was used to estimate the odds of the fetus having Down syndrome given different combinations of NB, PT, PT/NB ratio, and digits 2 and 3 measurements. The odds were used to calculate the risk of Down syndrome for each pregnant woman from her age and measurements.

RESULTS

The median PT MoM for unaffected fetuses and Down-syndrome fetuses was 1.12 vs. 1.35 (P < 0.0001). The median NB MoM for unaffected and Down-syndrome fetuses was 1.03 vs. 0.81 (P < 0.001) and the PT/NB ratio MoM for unaffected and Down-syndrome fetuses was 0.63 vs. 0.96 (P < 0.001). The respective median MoM values for digits 2 and 3 of the Down-syndrome fetuses were significantly smaller (0.81 vs. 0.93 and 0.89 vs. 0.95, respectively, P = 0.003). Only the PT/NB ratio and digit 2 were finally included in the logistic regression equation. Using a 1 in 200 risk cut-off, the observed sensitivity and false-positive rate were 76% and 6.7%, respectively.

CONCLUSION

Combining the PT/NB ratio and digit 2 measurements yielded a promising screening detection rate. Confirmation of our findings in a prospective study is needed before the method can be used clinically.

Randomised controlled trial of mammographic screening in women from age 40: predicted mortality based on surrogate outcome measures

A trial in the UK to study the effect on mortality from breast cancer of invitation for annual mammography from the age of 40–41, has randomised a total of 160 921 women in the ratio 1 : 2 to the intervention and control arms. All breast cancers diagnosed in the two arms have been identified, and the histology reviewed. This paper presents the results of an interim analysis using surrogate outcome measures to compare predicted breast cancer mortality in the two arms based on 1287 cases diagnosed to 31.12.1999. Due to earlier diagnosis, there is currently an 8% excess of invasive breast cancers in the intervention arm. The ratio of predicted deaths at 10 years in the intervention arm relative to the control arm, adjusted for this excess diagnosis, ranges from 0.89 (95% confidence interval (CI) 0.78–1.01) to 0.90 (95% CI 0.80–1.01). Screening from age 40 may result in a lower reduction in breast cancer mortality than that observed in other trials including women below age 50. This analysis based on surrogate outcome measures suggests that a reduction in breast cancer mortality may be observed in this trial. However, a number of assumptions have been necessary and firm conclusions must await the analysis of observed mortality from breast cancer.

Frequency and clinical consequences of extremely high maternal serum PAPP-A levels

A multicentre study was carried out to determine the frequency and clinical consequences of extremely high maternal serum pregnancy-associated plasma protein (PAPP)-A. There was a total of 79 pregnancies with PAPP-A exceeding 5.0 multiples of the gestation-specific median in a series of 46 776 pregnancies tested (0.2%) at the 7 collaborating centres. Five pregnancies were lost to follow-up, one miscarried and one with Noonan's syndrome was terminated. Of the remaining 72 that ended in a live birth, one infant had gastroschisis and five pregnancies had obstetric complications: pre-eclampsia, pregnancy-induced hypertension, gestational diabetes and two with growth retardation. Among women with high PAPP-A and no complications or adverse outcomes, there was no evidence of a substantial change in the levels of other Down syndrome markers or the extent of nuchal translucency. Three analytical methods were used to assay PAPP-A and yielded different frequencies of extremely high levels (0.05%, 0.4% and 0.6%) possibly owing to cross-reaction with another substance. We conclude that women with high PAPP-A can be reassured that there is no reason to suppose that the outcome of pregnancy will differ from those with normal levels, provided other markers are normal. If, as more centres move their Down syndrome screening practice to the first trimester, additional cases emerge with Noonan's syndrome or gastroschisis and raised PAPP-A, this advice will need to be modified.

Centre-specific ultrasound nuchal translucency medians needed for Down syndrome screening

Nuchal translucency (NT) measurements were compared between 13 centres participating in a multi-marker Down syndrome screening program. Results from 4765 women were analysed, and there were highly statistically significant between-centre differences after allowing for gestation (P < 0.0001). Examination of maternal serum marker levels, expressed in multiples of the median (MoM) for gestation, showed that this was not due to gestational errors. Regression analysis was carried out to derive an equation with a centre-specific component that could be used to express NT in MoMs. Use of this equation reduced the variance of logNT by 15% compared to a published equation. The equation can be readily modified for use in other centres.

Down's syndrome screening with nuchal translucency at 12(+0)-14(+0) weeks and maternal serum markers at 14(+1)-17(+0) weeks: a prospective study

BACKGROUND

Sonographic and biochemical methods for Down's syndrome screening have developed simultaneously, but independently. As a consequence, the rate of invasive procedures for fetal karyotyping has dramatically increased and become an important public health issue which needs to be controlled. One approach is to combine sonographic and biochemical results into a single risk assessment.

METHODS

In a multicentre interventional study, nuchal translucency (NT) was measured between 12(+0) and 14(+0) weeks of gestation. Maternal serum markers (MSM) were measured between 14(+1) and 17(+0) weeks of gestation. Karyotyping was advised when: (i) NT was > or =3 mm; or (ii) the MSM-related risk was > or =1 in 250 at term. Karyotyping was delayed until after a maternal blood sample had been taken. NT and MSM were expressed as multiples of the medians (MoMs), and risks were calculated and tailored to the study population. A combined risk for NT and MSM was estimated retrospectively. Costs per case diagnosed, and the cost per case averted were calculated for the three screening strategies.

RESULTS

A total of 9444 women was screened. Twenty-one fetuses (0.22%) had Down's syndrome, whilst 326 women (3.4%) were lost to follow-up. Among 9118 women followed up, 5506 had both NT and MSM, 821 had only NT, and 2791 had only MSM. Median maternal age was 30.5 years. False-positive rates for NT, MSM and NT combined with MSM were 3.0, 5.8 and 0.23% respectively. The false-positive rate generated by a sequential two-stage screening was 8.6%. Detection rates of Down's syndrome were 62 and 55% for NT and MSM respectively. Seven cases with Down's syndrome (35%) had raised NT and MSM, and 17 (81%) had either raised NT, MSM, or both. For a 5% false-positive rate, detection rates were 55 and 80% for NT alone and for combined NT and MSM respectively. Ultrasound alone appears to be more cost-effective ( pound50 per case diagnosed) than both tests ( pound61 per case diagnosed).

CONCLUSIONS

The study results suggest a 25% increase in the detection rate of Down's syndrome using a combination of NT measurement at 12(+0)-14(+0) weeks and MSM at 14(+1)-17(+0) weeks for a 5% false-positive rate, with modest increase in cost.

Familial Down syndrome: evidence supporting cytoplasmic inheritance

The frequently observed familial aggregation of Down syndrome (DS) 47,+21 and other aneuploidies and the phenomenon of double aneuploidy involving DS cannot be accounted for by chance alone. To clarify possible aetiological factors, pedigrees from all 7 affected families with repeated marriages referred to two regional genetics centres were examined. In each case the recurrence of aneuploidy was on the mother's side (p<0.01). Such a pattern suggests cytoplasmic inheritance of a risk factor. The hypothesis that mitochondrial DNA mutations have a role in the aetiology of DS is supported by other observations as well as by theoretical considerations.

Cystic Fibrosis and Fragile X Syndrome The Arguments for Antenatal Screening

The ultimate public health aim of genetic screening is prevention. This can be achieved by reducing birth prevalence through primary or secondary methods such as pre-conceptional or antenatal screening. Tertiary prevention by neonatal screening is also an option where there is direct unbiased evidence for a substantial improvement in prognosis. In addition to this, the information provided during screening is also of value, enabling individuals to make choices that otherwise would not have been available. Having elucidated the natural histories and genetic defects underlying two common, serious genetic disorders, cystic fibrosis and fragile X syndrome, considerable efforts have been channelled into ascertaining the most efficacious method of prevention. To date there is only indirect evidence to suggest that neonatal screening improves prognosis in cystic fibrosis. Similarly, treatment for fragile X syndrome is limited and therefore early identification of the disorder by neonatal screening is unlikely to improve long term outlook. Thus the focus of this review is on primary and secondary preventive methods.

Integrating antenatal Down's syndrome screening

Statistical modelling is used to predict screening detection and false-positive rates for policies using different marker combinations and screening modalities. Parameters are derived wherever possible from meta-analyses. Screening with four serum markers yields a similar detection rate in the first trimester as it does in the second, and both have a similar detection rate to that of ultrasound nuchal translucency screening. Ultrasound anomaly screening has a low detection rate. The integration of the different screening modalities can yield very high detection rates. Some methods of integration are preferable to others. The concurrent use of first trimester serum markers and ultrasound nuchal translucency is the most practical. The combination of three modalities with nondisclosure of the intermediate results is more efficient, but the gain in detection is too small to warrant the wait for up to 4 weeks for results. The sequential use of modalities with intermediate disclosure is more practical but will generate higher false-positive rates.

Quality of written information used in Down syndrome screening

A qualitative assessment was performed on 81 leaflets used in maternal serum Down syndrome screening from National Health Service (NHS) obstetric units and private screening services. Quality was assessed by factual content, presentation and reading ease and this was amalgamated into a single overall score expressed as a percentage of the maximum possible score. Eleven (14%) leaflets included all eight factual items recommended by the Royal College of Obstetricians and Gynaecologists (RCOG); only one included these and a further nine items recognised as important to the consumer. Three (4%) leaflets contained information that was incorrect and 17 (21%) that was misleading or inconsistent. Using published criteria six (7%) leaflets were well presented and ten (12%) were fairly easy to read. The average reading age was 13-14 years. The overall quality score showed that five leaflets had 80% or more of the total possible score. However a substantial number, 15 (19%), were totally unacceptable having scores of 40% or less. In general the quality of leaflets used in the UK is considered poor. A national peer-reviewed leaflet should be prepared which can be modified to suit local policy.

Maternal serum human chorionic gonadotrophin levels in systemic lupus erythematosus and antiphospholipid syndrome

Maternal serum human chorionic gonadotrophin (hCG) levels were measured during the second and the third trimesters of pregnancy in patients with either systemic lupus erythematosus (SLE) or primary antiphospholipid syndrome (APS). All results were expressed in multiples of the gestation-specific normal medians (MoM). The median MoM level in 17 samples from SLE patients was 1.48 compared with 0.79 MoM in 99 controls of similar gestation (p < 0.002, Wilcoxon Rank sum test). In contrast the median MoM level in 19 samples from primary APS patients was only 1.14. These preliminary findings should be further studied to evaluate the implications for Down syndrome screening, detection of SLE cases during pregnancy and the prediction of adverse outcome in SLE gestations.

Use of videotapes for viewing at home to inform choice in Down syndrome screening: a randomised controlled trial

A randomised trial was carried out to assess the effect of a Down syndrome screening video on test uptake, knowledge and psychological stress. A total of 2000 women referred for antenatal care were allocated to two equal groups: one to be sent a video to their home, before their hospital booking visit, and a control group. All women also received screening information in the form of a leaflet before booking and from a midwife at booking. The video had no effect on the screening uptake rate: 638/993 (64.2%) and 652/1007 (64.7%) in the video and control groups, respectively. Women were requested to return the video for reuse in other pregnancies and 612 (62%) did so. A subset of 1200 women were selected to be posted at 17-19 weeks' gestation a self-completed questionnaire to assess the psychological endpoints. Knowledge of screening was increased in the video group with a mean score of 7.3 compared with 6.7 in the controls, a statistically significant difference (t=3.24, p=0.0005). There were no significant differences between the groups in specific worries about abnormalities in the baby, and general anxiety. We conclude that a video can increase knowledge without affecting the uptake of the test, or psychological stress.