Identification of fragile X pre-mutation carriers in the Chinese obstetric population using a robust FMR1 polymerase chain reaction assay: implications for screening and prenatal diagnosis

INTRODUCTION

There is significant morbidity associated with fragile X syndrome. Unfortunately, most maternal carriers are clinically silent during their reproductive years. Because of this, many experts have put forward the notion of preconception or prenatal fragile X carrier screening for females. This study aimed to determine the prevalence of fragile X syndrome pre-mutation and asymptomatic full-mutation carriers in a Chinese pregnant population, and the distribution of cytosine-guanine-guanine (CGG) repeat numbers using a robust fragile X mental retardation 1 (FMR1) polymerase chain reaction assay.

METHODS

This was a cross-sectional survey in prospectively recruited pregnant women from a university hospital in Hong Kong. Chinese pregnant women without a family history of fragile X syndrome were recruited between April 2013 and May 2015. A specific FMR1 polymerase chain reaction assay was performed on peripheral blood to determine the CGG repeat number of the FMR1 gene. Prenatal counselling was offered to full-mutation and pre-mutation carriers.

RESULTS

In 2650 Chinese pregnant women, two individuals with pre-mutation alleles (0.08%, one in 1325) and one asymptomatic woman with full-mutation (0.04%, one in 2650) alleles were identified. The overall prevalence of pre-mutation and full-mutation alleles was 0.11% (1 in 883). Furthermore, 30 (1.1%) individuals with intermediate alleles were detected. In the 2617 women with normal CGG repeats, the most common CGG repeat allele was 30.

CONCLUSIONS

The overall prevalence of pre-mutation and asymptomatic full-mutation carriers in the Chinese pregnant population was one in 883, detected by a new FMR1 polymerase chain reaction assay.

Non-invasive prenatal testing for trisomies 21, 18 and 13: clinical experience from 146,958 pregnancies

OBJECTIVES

To report the clinical performance of massively parallel sequencing-based non-invasive prenatal testing (NIPT) in detecting trisomies 21, 18 and 13 in over 140,000 clinical samples and to compare its performance in low-risk and high-risk pregnancies.

METHODS

Between 1 January 2012 and 31 August 2013, 147,314 NIPT requests to screen for fetal trisomies 21, 18 and 13 using low-coverage whole-genome sequencing of plasma cell-free DNA were received. The results were validated by karyotyping or follow-up of clinical outcomes.

RESULTS

NIPT was performed and results obtained in 146,958 samples, for which outcome data were available in 112,669 (76.7%). Repeat blood sampling was required in 3213 cases and 145 had test failure. Aneuploidy was confirmed in 720/781 cases positive for trisomy 21, 167/218 cases positive for trisomy 18 and 22/67 cases positive for trisomy 13 on NIPT. Nine false negatives were identified, including six cases of trisomy 21 and three of trisomy 18. The overall sensitivity of NIPT was 99.17%, 98.24% and 100% for trisomies 21, 18 and 13, respectively, and specificity was 99.95%, 99.95% and 99.96% for trisomies 21, 18 and 13, respectively. There was no significant difference in test performance between the 72,382 high-risk and 40,287 low-risk subjects (sensitivity, 99.21% vs. 98.97% (P = 0.82); specificity, 99.95% vs. 99.95% (P = 0.98)). The major factors contributing to false-positive and false-negative NIPT results were maternal copy number variant and fetal/placental mosaicism, but fetal fraction had no effect.

CONCLUSIONS

Using a stringent protocol, the good performance of NIPT shown by early validation studies can be maintained in large clinical samples. This technique can provide equally high sensitivity and specificity in screening for trisomy 21 in a low-risk, as compared to high-risk, population.

Diagnostic accuracy of the BACs-on-Beads™ assay versus karyotyping for prenatal detection of chromosomal abnormalities: a retrospective consecutive case series

OBJECTIVE

To evaluate the diagnostic performance of the BACs-on-Beads(™) (BoBs(™)) assay for prenatal detection of chromosomal abnormalities.

DESIGN

Retrospective study.

SETTING

Tertiary prenatal diagnosis centre.

POPULATION

Women referred for prenatal diagnosis.

METHODS

We retrieved 2153 archived DNA samples collected between January 2010 and August 2011 for the BoBs(™) assay. These samples had previously been tested by quantitative fluorescence polymerase chain reaction (QF-PCR) and karyotyping. In the BoBs(™) assay a sample was defined as normal disomic when the ratio of the fluorescence intensities in a chromosome locus lay within the threshold (mean ratio ± 2SD), and as deleted or duplicated when the ratio was below the lower threshold (0.6-0.8) or above the upper threshold (1.3-1.4), respectively. The BoBs(™) results were further validated by microarray and compared in a blinded manner with the original QF-PCR and karyotyping results.

MAIN OUTCOME MEASURES

Concordance of any numerical, structural, and submicroscopic chromosomal abnormalities between the methods.

RESULTS

BACs-on-Beads(™) was similar to karyotyping and QF-PCR in detecting trisomy 13, trisomy 18, trisomy 21, and sex chromosomal aneuploidies, and superior to QF-PCR in detecting major structural abnormalities (53.3 versus 13.3%) and mosaicism (28.6 versus 0%) involving chromosomal abnormalities other than the common aneuploidies. BoBs(™) detected six microdeletion syndromes missed by karyotyping and QF-PCR; however, BoBs(™) missed two cases of triploidy identified by QF-PCR. Therefore, the sensitivity of BoBs(™) is 96.7% (95% CI 92.6-98.7%), and its specificity is 100% (95% CI 99.8-100%).

CONCLUSIONS

BACs-on-Beads(™) can replace QF-PCR for triaging in prenatal diagnosis, and gives a better diagnostic yield than current rapid aneuploidy tests.

Non-invasive prenatal testing for fetal chromosomal abnormalities by low-coverage whole-genome sequencing of maternal plasma DNA: review of 1982 consecutive cases in a single center

OBJECTIVE

To review the performance of non-invasive prenatal testing (NIPT) by low-coverage whole-genome sequencing of maternal plasma DNA at a single center.

METHODS

The NIPT result and pregnancy outcome of 1982 consecutive cases were reviewed. NIPT was based on low coverage (0.1×) whole-genome sequencing of maternal plasma DNA. All subjects were contacted for pregnancy and fetal outcome.

RESULTS

Of the 1982 NIPT tests, a repeat blood sample was required in 23 (1.16%). In one case, a conclusive report could not be issued, probably because of an abnormal vanished twin fetus. NIPT was positive for common trisomies in 29 cases (23 were trisomy 21, four were trisomy 18 and two were trisomy 13); all were confirmed by prenatal karyotyping (specificity=100%). In addition, 11 cases were positive for sex-chromosomal abnormalities (SCA), and nine cases were positive for other aneuploidies or deletion/duplication. Fourteen of these 20 subjects agreed to undergo further investigations, and the abnormality was found to be of fetal origin in seven, confined placental mosaicism (CPM) in four, of maternal origin in two and not confirmed in one. Overall, 85.7% of the NIPT-suspected SCA were of fetal origin, and 66.7% of the other abnormalities were caused by CPM. Two of the six cases suspected or confirmed to have CPM were complicated by early-onset growth restriction requiring delivery before 34 weeks. Fetal outcome of the NIPT-negative cases was ascertained in 1645 (85.15%). Three chromosomal abnormalities were not detected by NIPT, including one case each of a balanced translocation, unbalanced translocation and triploidy. There were no known false negatives involving the common trisomies (sensitivity=100%).

CONCLUSIONS

Low-coverage whole-genome sequencing of maternal plasma DNA was highly accurate in detecting common trisomies. It also enabled the detection of other aneuploidies and structural chromosomal abnormalities with high positive predictive value.

Relationship between age and prevalence of hepatitis B infection in first-year university students in Hong Kong

PURPOSE

To determine the effect of age on the prevalence of hepatitis B virus (HBV) infection during a routine screening programme of first-year students enrolled in Health Sciences Studies at the Chinese University of Hong Kong from 2001 to 2009.

METHODS

In a retrospective cohort study, data on the hepatitis B surface antigen (HBsAg) status was retrieved from the University Health Service and analysed according to the age of the student at testing and year of birth.

RESULTS

Of the 2,688 students enrolled in the study group, 79 (2.9 %) tested positive for HBsAg. The prevalence increased significantly from 0.9, 2.3, 4.3 to 5.5 % for those tested at age ≤ 18, 19, 20 and ≥ 21 years, respectively (p < 0.001). On logistic regression analysis, taking age ≤ 18 years and year of birth before 1983 (before the availability of HBV vaccination) as the reference group, HBV infection increased progressively with age, with an adjusted odds ratio of 3.36 [95 % confidence interval (CI) 1.01-11.23], 6.04 (95 % CI 1.74-20.98) and 11.61 (95 % CI 3.20-42.13) for age 19, 20 and ≥ 21 years, respectively. There was no significant change in the odds ratio after adjustment for the year of birth before and after introduction of the vaccination programme.

CONCLUSION

Among the university students enrolled in our study, the overall prevalence of HBV infection before and after the introduction of HBV vaccination was lower than the 10 % found in the general population. There was, however, a significant progressive increase with age at testing from ≤ 18 to ≥ 21 years, suggesting a previously overlooked contribution of horizontal transmission to the high prevalence of HBV infection found in our adult population.

Intrapleural injection of OK-432 as the primary in-utero treatment for fetal chylothorax

Chylothorax is a rare congenital condition associated with significant perinatal mortality and morbidity. Previous treatments with repeated thoracocentesis or thoracoamniotic shunting were technically demanding, and associated with significant procedure-related complications and neonatal complications. Here we report the first successful case in Hong Kong treated by a simple and effective intervention, namely pleurodesis with OK-432, in a fetus presenting at 20 weeks of gestation with bilateral pleural effusion.

A novel way of visualizing the ductal and aortic arches by real-time three-dimensional ultrasound with live xPlane imaging

OBJECTIVE

To describe a novel method of visualizing the ductal and aortic arches by real-time three-dimensional echocardiography with live xPlane imaging.

METHODS

Live xPlane imaging was used to display the ductal- and aortic-arch views in 107 women with singleton pregnancies, including seven cases with suspected congenital heart defects (CHDs). The three vessels and trachea (3VT) view was obtained in such an orientation that either the pulmonary artery or the aorta was parallel to the direction of the ultrasound beam. The xPlane reference line was then placed across the targeted vessel, which in a normal case would provide an image of the corresponding arch view as a dual-image display.

RESULTS

Once the 3VT view had been obtained, live xPlane imaging showed the aortic and ductal arches in all 100 normal cases. In seven cases with suspected CHD, the 3VT view was abnormal in five cases and normal in the other two. However, the ductal-arch view demonstrated by live xPlane imaging was abnormal in five cases of conotruncal anomalies and normal in two cases in which conotruncal anomalies were excluded. CHDs were confirmed at autopsy following termination of pregnancy in five cases and on postnatal echocardiography in one case. The heart was found postnatally to be normal in one case of suspected CHD; in this case live xPlane imaging showed that the observed abnormal 3VT view was caused by a tortuous course of the thoracic aorta associated with an abnormal diaphragm.

CONCLUSION

Live xPlane imaging is a novel and relatively simple method of visualizing the ductal- and aortic-arch views, and may potentially be a useful tool in the screening of fetal conotruncal and aortic-arch anomalies.

Effect of image settings on nuchal translucency thickness measurement by a semi-automated system

OBJECTIVE

To investigate whether pre- and post-processing image settings affect NT measurements made by a semi-automatic method (SAM).

METHODS

Different image settings (e.g. gain) were either adjusted one at a time on images that had been obtained during fetal NT scans (post-processing, n = 66), or adjusted one at a time during live scanning and image acquisition of the adult posterior tibial artery (pre-processing group, n = 91). The NT and luminal diameter of the posterior tibial artery, respectively, were measured by SAM on all original and adjusted images.

RESULTS

Alteration of the image settings resulted in a statistically significant effect on the measurements taken by SAM, with an average pair difference ranging from 0.001 mm to 0.139 mm. Most of the differences were small and therefore the clinical impact would be negligible. The pair differences were greatest with a very high contrast setting, or without tissue harmonic imaging (THI); the paired difference in measurement in those with vs those without THI was more than 0.1 mm in over 40% of cases.

CONCLUSIONS

Measurements made by SAM are affected by image settings.

Identification of submicroscopic chromosomal aberrations in fetuses with increased nuchal translucency and apparently normal karyotype

OBJECTIVE

Fetal nuchal translucency (NT) is assessed by ultrasonography as a screening tool for aneuploidy at 11 to 13 + 6 weeks' gestation. Fetuses with increased NT but apparently normal karyotype are still at higher risk of structural abnormality and a range of genetic syndromes, which may be related to major and submicroscopic chromosomal abnormalities. The aim of this study was to report the prevalence of submicroscopic chromosomal abnormalities in a cohort of apparently euploid fetuses that presented with increased NT.

METHODS

DNA was extracted from stored chorionic villus samples from fetuses found to have increased NT (> 3.5 mm) during first-trimester screening. These samples were examined by microarray-based comparative genomic hybridization (aCGH) using a 44K oligonucleotide array specifically constructed for prenatal screening. Variations in copy number (CNVs) were reported after excluding known non-pathogenic variants and after validation with multiplex ligation-dependent probe amplification (MLPA) or real-time quantitative polymerase chain reaction (qPCR). The prevalence of pathogenic CNVs is reported and the association with NT and other ultrasound findings described.

RESULTS

CNVs were reported in 6/48 (12.5%) cases by aCGH and the microdeletions or microduplications ranged from 1.1 to 7.9 Mb. Five of these were validated by MLPA/real-time qPCR and four (8.3%) were considered to be pathogenic and clinically significant. The incidence of pathogenic CNVs was 20.0% (2/10) among those cases with other sonographic anomalies and 5.3% (2/38) among those without.

CONCLUSION

aCGH allows detection of submicroscopic chromosomal abnormalities, the prevalence of which may be increased in fetuses with NT > 3.5 mm and an apparently normal karyotype.

Correlation between maternal hepatitis B surface antigen carrier status with social, medical and family factors in an endemic area: have we overlooked something?

PURPOSE

Hepatitis B virus (HBV) infection is endemic in many countries, but the risk factors for HBV carriage in the obstetric population are unclear.

METHODS

A survey on 1,580 women attending the antenatal clinic in an endemic region was conducted in order to examine the prevalence of and factors associated with maternal HBV carriage, including socio-demographic, medical, and previous obstetrical and family history, by means of a questionnaire.

RESULTS

The prevalence of maternal HBV carriage was 9.1%, and 4.8% of women with a history of hepatitis B vaccination were found to be HBV carriers. Factors associated with maternal HBV carriage were residency status (adjusted odds ratio [aOR] 3.65 for immigrants; aOR 7.62 for non-residents), positive family history (aOR 3.72 for infected mother; aOR 5.36 for other family members), no previous vaccination (aOR 4.39) and having previous HBsAg testing (aOR 2.26).

CONCLUSIONS

The findings suggest that there was probably an overlooked role of horizontal transmission within the family setting in addition to perinatal transmission in determining the likelihood of HBV infection in our obstetric population. Reconfirmation of hepatitis B status might be necessary among individuals with a history of vaccination to ensure the effectiveness of their immunoprotection.

Head-to-body delivery interval and risk of fetal acidosis and hypoxic ischaemic encephalopathy in shoulder dystocia: a retrospective review

OBJECTIVE

To examine the association between head-to-body delivery interval (HBDI) and cord arterial pH and base excess (BE), and the risk of development of hypoxic ischaemic encephalopathy (HIE).

DESIGN

Retrospective review.

SETTING

A university hospital.

POPULATION

Pregnancies complicated with shoulder dystocia during the period 1995-2009.

METHODS

Cases were identified from a search of the hospital electronic delivery records. Cord arterial pH and BE, and the incidence of HIE and perinatal death, were retrieved from medical records and correlated with HBDI, birth weight, mode of delivery and presence of nonreassuring fetal heart rate pattern and maternal diabetes using univariate analysis, followed by multivariate analysis.

MAIN OUTCOME MEASURES

Any association between cord pH and HBDI.

RESULTS

Of the 200 cases identified, the mean (standard deviation) HBDI was 2.5 minutes (1.5 minutes). Both HBDI and the presence of nonreassuring fetal heart rate pattern were independent factors for pH, and HBDI was the only significant factor for BE. Arterial pH dropped at a rate of 0.011 per minute [95% confidence interval (95% CI), 0.017-0.004; P = 0.002] with HBDI. The mode of delivery, birth weight and maternal diabetes did not affect blood gas levels. The respective risks of severe acidosis (pH < 7) and HIE with HBDI of <5 minutes were 0.5% and 0.5% versus 5.9% and 23.5% with HBDI ≥ 5 minutes.

CONCLUSIONS

Cord arterial pH drops with HBDI during shoulder dystocia, but the risk of acidosis or HIE is very low with HBDI < 5 minutes.

Chronic hepatitis B virus infection and rubella susceptibility in pregnant women

Increased rubella susceptibility has been shown in subjects from the Asian-Pacific region where chronic hepatitis B virus (HBV) infection is endemic. This study was performed to explore the relationship between chronic HBV infection and rubella susceptibility in the obstetric population. We conducted a retrospective cohort study on 50556 pregnant women delivered in a university obstetric unit from January 1998 to June 2008. The incidence of rubella susceptibility according to maternal HBV carrier status was examined. HBV infection and rubella susceptibility were found in 5105 (10.1%) and 6102 (12.1%) women, respectively. Rubella susceptibility was more common in women with HBV (13.1%vs 12.0%, P = 0.017), even after adjusting for other confounding factors (odds ratio 1.11, 95% confidence interval 1.01-1.21). Advancing age was associated with progressively decreasing odds of rubella susceptibility, from 0.48 at age 20-24 years to 0.34 at age ≥ 40 years in women without HBV infection, but had no effect in women with hepatitis B. In conclusion, our study is the first to demonstrate an association between chronic HBV infection with rubella susceptibility. Further studies are warranted to confirm whether chronic HBV infection, especially that acquired by vertical transmission, may impair the immune response to rubella vaccine or natural infection throughout the reproductive age.

Real-time three-dimensional ultrasound with Live xPlane imaging assists first-trimester acquisition of a true midsagittal section

OBJECTIVE

To determine whether real-time three-dimensional (3D) ultrasound with Live xPlane imaging, which enables the simultaneous display of two real-time high-quality image planes, can assist both operators certified by The Fetal Medicine Foundation (FMF) and non-FMF-certified operators in acquiring a true midsagittal plane in the first trimester.

METHODS

Eight operators, four of them FMF certified (FMF group) and the other four not (non-FMF group), were asked to acquire a fetal image that they believed to represent the true midsagittal plane using real-time 3D ultrasound with Live xPlane imaging as guidance. Each operator was asked to obtain such an image five times from each of five patients. A total of 200 images from 40 patients were obtained and stored for subsequent analysis. All pregnancies were between 11 + 0 and 13 + 6 weeks of gestation. The angle between the falx cerebri and vertical axis (angle of deviation) was then measured by a single operator. A true midsagittal section was defined as an angle of deviation equal to 0 degrees. The angle of deviation and the time taken to acquire each image were compared between FMF and non-FMF groups.

RESULTS

The median angle of deviation for each operator ranged from 1.2 degrees to 3.4 degrees. There was no significant difference in this angle between those who were FMF certified and those who were not (2.0 degrees vs. 2.2 degrees, P = 0.463). The interquartile range of the angle of deviation was also similar between the FMF- and non-FMF-certified operators. Although the time taken for image acquisition was longer among the non-FMF-certified operators (median, 45.5 s vs. 32.0 s), this difference did not reach statistical significance (P = 0.107).

CONCLUSION

Live xPlane imaging can provide a tool to assist the acquisition of a true midsagittal plane and to determine how true a 'midsagittal' plane really is.

Fetoscopic laser photocoagulation in the management of twin-twin transfusion syndrome: local experience from Hong Kong

OBJECTIVE

To review the perinatal outcome of monochorionic twin pregnancies treated by fetoscopic laser coagulation for twin-twin transfusion syndrome.

DESIGN

Retrospective study.

SETTING

A university teaching hospital in Hong Kong.

PATIENTS

Thirty consecutive cases of fetoscopic laser coagulation of placental anastomoses for twin-twin transfusion syndrome performed in a single centre.

MAIN OUTCOME MEASURES

Operative complications and perinatal survival rates.

RESULTS

The median gestational age at initial presentation, laser photocoagulation, and delivery were 22 (range, 16-27) weeks, 23 (18-28) weeks, and 32 (21-37) weeks, respectively. To improve the visualisation, in three cases amnio-exchange was undertaken; the procedure was abandoned in two due to poor visualisation. The overall fetal survival rate, the double infant survival rate, and survival rate for at least one twin were 72% (43/60), 60% (18/30), and 83% (25/30), respectively. The most common peri-operative complication was bleeding from the uterine wall into the amniotic cavity, which affected three (10%) patients.

CONCLUSIONS

Our results of fetoscopic laser surgery for twin-twin transfusion syndrome were similar to those in specialised centres in other countries.

Comparison of likelihood ratios of first-trimester nuchal translucency measurements: multiples of median, delta or mixture

OBJECTIVE

To compare the likelihood ratios (LR) determined for a measured nuchal translucency (NT) using the multiples of the median (MoM), delta-NT and mixture model approaches.

METHODS

This was a retrospective study of singleton pregnancies with known outcome screened at the 12(th) week of pregnancy between January 2006 and May 2008. NT, crown-rump length (CRL) and LR for trisomy 21 using the delta-NT approach (LRNT-delta) were extracted from The Fetal Medicine Foundation trisomy 21 risk-calculation software database. NT measurements were converted into their equivalent MoM by dividing by the expected CRL-specific median NT. LR for trisomy 21 based on the MoM (LRNT-MoM) of each case was then calculated as the ratio of the Gaussian probability density functions using published trisomy 21 risk-screening parameters. The LR using the mixture model (LRNT-mixture) was calculated as the ratio of individual composite probability densities reported for trisomy 21 and unaffected pregnancies. The intraclass correlation coefficient (ICC) was used to assess the agreement between the three different approaches while the paired t-test was used to perform pairwise comparisons.

RESULTS

Of the 5907 pregnancies with known outcome, 14 had trisomy 21. The ICC between the three approaches to determining an LR was 0.947 (95% CI, 0.943-0.951; P < 0.0001). Pairwise comparison indicated that differences between LR were statistically significant (P < 0.0001). Likelihood ratios determined via the delta-NT model were in general greater than those produced by both the mixture model (z = 5.58, P < 0.0001) and the MoM approaches (z = 32.8, P < 0.0001). For a 5% false-positive rate the detection rate of trisomy 21 (DR) was 78.6% (95% CI, 57.1-99.9%) The screen positive thresholds to achieve this DR were 1 : 200 for the delta-NT approach, 1 : 220 for the mixture approach and 1 : 290 for the MoM approach.

CONCLUSION

No single method of determining NT-associated LR outperformed the others in its ability to detect a trisomy 21-affected pregnancy.

Learning curve in measurement of fetal frontomaxillary facial angle at 11-13 weeks of gestation

OBJECTIVE

To determine the number of ultrasound examinations required to train sonographers to accurately measure the fetal frontomaxillary facial (FMF) angle at 11-13 weeks of gestation.

METHODS

Eight sonographers accredited for nuchal translucency thickness (NT) measurement (and with different levels of experience) were trained to measure the fetal FMF angle using specially acquired three-dimensional (3D) volumes. Training was provided in cycles, and each cycle consisted of a training period on 20 randomly selected cases followed by an examination using 10 randomly selected cases. During training, the sonographer was informed of the true FMF angle value after each FMF angle measurement on a case-by-case basis. During examination, the difference between the measured and the true values of the FMF angle (i.e. the delta angle) was calculated. A measurement was considered accurate if the delta angle was less than 5 degrees . The sonographer was considered to be competent and the training finished if all 10 examination cases satisfied this criterion. Otherwise, the sonographer would undergo further cycles of training-examination, until he/she became competent.

RESULTS

The number of training cases required for a sonographer to become competent was 40 for two sonographers, 60 for one, 80 for one, 100 for two, 120 for one and 140 for one, with a median of 90. The median number of failed cases reduced from 2.5 (out of 10) at the first cycle to 0 by the 7(th) cycle. As training cycles increased, the mean angle deviation and measurement time required both reduced significantly. The average delta angle of the passing examination cycle was 2.06 +/- 1.40 degrees . The number of training cases required to become competent in FMF angle measurement was 40 for the two most experienced trainees and 80, 120 and 140 for the three least experienced ones.

CONCLUSIONS

We have demonstrated that competence in FMF angle measurement was achieved after a median number of 90 cases, with a range of up to 140. The number required was substantially lower, at 40 cases, among those with extensive experience of NT measurement.

Implications of the relationship between maternal age and parity with hepatitis B carrier status in a high endemicity area

This study aimed to examine the prevalence of maternal hepatitis B virus (HBV) infection in the past 10 years and the age- and parity-specific incidences for evidence of control of HBV infection in the female reproductive population. We conducted a retrospective cohort study on 58 736 consecutive pregnant women delivered from July 1998 to June 2008. Maternal HBV status and demographic data were retrieved from a computerized database for analysis by year, age, year of birth and parity. A total of 5788 (10.1%) women had HBV infection, and the annual prevalence was around 10% throughout. When categorized by maternal age into six 5-year cohorts, the incidence increased from 6.8% in the <20 years cohort to 10.8% in the 20-24 and 25-29 year cohorts, then declined to 9.3% in the > or =40 years cohort (P < 0.001). When categorized by year of birth into 5-year cohorts, the incidence varied from 9.2% for the 1965-1969 cohort to 11.3% in the 1980-1984 cohort, which then declined to 7.3% in the > or =1985 cohort (P < 0.001). Multiparas had higher incidence when compared with nulliparas overall (10.5% vs 9.6%, P = 0.001), and significantly higher incidences for the 25-29 year (P = 0.009), 30-34 year (P < 0.001) and 35-39 year (P = 0.032) cohorts when analysed by age. In conclusion, the prevalence of maternal HBV infection remained constant at 10% for the past decade. The changes in relation to age and parity suggested that horizontal transmission, probably by sexual contact, had played an important role in maintaining the same prevalence as reported from Hong Kong 20 years ago.

Comparison of first-trimester contingent screening strategies for Down syndrome

OBJECTIVE

To assess the relative performance of a multi-stage first-trimester screening protocol for fetal Down syndrome.

METHODS

Data from 10,767 women who underwent combined ultrasound and biochemistry (BC) screening in the first trimester were reanalyzed using a contingent model approach. Amongst the 10,854 fetuses with known outcome, 32 had Down syndrome, 232 had other abnormalities and 10,590 were unaffected. Nuchal translucency (NT), BC and combined (NT-BC) gestational age-specific risks were calculated for each individual using The Fetal Medicine Foundation risk calculation algorithms (Mixture Model and Biochemistry). Individual patients were categorized as at low, high or intermediate risk according to one of the following three strategies. In 'Strategy-NT-BC' initial screening was performed using both NT and BC. In 'Strategy-BC' initial screening was undertaken using maternal serum markers followed by NT assessment in those with an intermediate risk (1 : 51 < risk <or= 1:1000) while in 'Strategy-NT' initial screening was undertaken using NT followed by serum marker assessment in those with an intermediate risk (1 : 51 < risk <or= 1:1000). The nasal bone was assessed in those with an intermediate risk as the final stage in each of the three strategies. Those with an adjusted risk of 1 in 100 or higher after nasal bone assessment were reclassified as high risk. Detection and false-positive rates were compared between differing strategies in our local population, and this analysis was also performed with the maternal age for our population standardized to the distribution found in England and Wales.

RESULTS

In our local population the detection rate for a 5% false-positive rate using a combined screening policy (NT-BC) was 88% (95% CI, 75.3-98.9%), and 2.3% had an absent nasal bone. The respective detection rate and false-positive rate of the three multi-stage screening strategies were: Strategy-NT-BC: 87.5 and 2.5%; Strategy-BC: 87.5 and 5%; Strategy-NT: 84.4 and 2.9%. In the contingent Strategy-BC only 29% of those initially screened using serum markers required an NT scan. If the model were applied to a hypothetical obstetric population standardized to the maternal age distribution in England and Wales, the detection and false-positive rates of the same three screening strategies would be: Strategy-NT-BC: 86.2 and 1.9%; Strategy-BC: 82.8 and 4%; Strategy-NT: 75.8 and 2.3%, respectively.

CONCLUSION

First-trimester contingent screening provides detection and false-positive rates comparable to those achieved using combined screening, but could be used to significantly reduce the number of scans performed.

A survey of prenatal first-trimester aneuploidy screening among Hong Kong specialist obstetricians

OBJECTIVES

To determine the background, qualifications, and certification status of specialists currently performing first trimester screening in Hong Kong, the extent of their participation (and the laboratories they use) in quality assurance programmes, and their willingness to provide follow-up data for auditing purposes.

DESIGN

Questionnaire survey.

SETTING

Hong Kong.

PARTICIPANTS

A survey was mailed to all registered Hong Kong specialist obstetricians. Results were reported using descriptive statistics.

RESULTS

The response rate was 32% (106/331). Overall, 73% offered universal screening to all pregnant women. The majority (72%) most commonly performed first trimester screening for their patients. Sixty-six (62%) of the respondents performed nuchal translucency scanning; only 30 (45%) were accredited by a recognised body to perform such scans. Only 33% of the relevant laboratories used by specialists participated in external quality assurance programmes specific to Down's syndrome screening undertaken by a third party organisation.

CONCLUSIONS

According to our data, first trimester screening has become one of the most common screening strategies for Down's syndrome in Hong Kong, but there is a need to assess the quality of such prenatal screening for aneuploidy to ensure its efficacy.

Change in prevalence of group B Streptococcus maternal colonisation in Hong Kong

OBJECTIVES

To re-examine the prevalence of group B Streptococcus colonisation in our antenatal population, and identify demographic factors associated with carriage.

DESIGN

Prospective observational study.

SETTING

A tertiary obstetrics unit in Hong Kong.

PARTICIPANTS

A total of 1002 pregnant women were recruited at the booking clinic in a tertiary obstetrics unit in Hong Kong. High and low vaginal swabs and rectal swabs were taken for group B Streptococcus culture. Demographic data and delivery outcomes of the recruits were analysed.

RESULTS

The prevalence of group B Streptococcus colonisation in our antenatal population was 10.4%. The majority of carriers were identified by low vaginal swabs (78%), while high vaginal swabs and rectal swabs only identified 31% and 30% of the carriers, respectively. Professional women yielded a higher carrier rate than housewives (21% vs 10%, P=0.03). There was no increase in preterm delivery rate in group B Streptococcus carriers.

CONCLUSIONS

We noted a dramatic increase in the prevalence of group B Streptococcus colonisation in the Hong Kong pregnant population at their booking visit. Professional women had a higher colonisation rate compared to other groups.

Real-time three-dimensional echocardiography using a matrix probe with live xPlane imaging of the interventricular septum

OBJECTIVE

To describe a technique to rapidly visualize the in-plane view of the fetal interventricular septum (IVS) to enable the identification of a ventricular septal defect (VSD).

METHODS

One hundred and fifty-one women were invited to participate after their routine fetal morphology scan, including four suspected to have congenital cardiac defects which were confirmed postnatally. A standard examination protocol using real-time three-dimensional (3D) echocardiography with live xPlane imaging was developed. The ability of this new technology to examine the ventricular septum was investigated.

RESULTS

The in-plane view of the fetal IVS was visualized successfully in 150 (99.3%) cases by real-time 3D echocardiography with live xPlane imaging, including 82 (54.3%) cases with the spine posterior and 68 (45.7%) cases with the spine anterior. The in-plane view of the IVS successfully visualized the VSDs in three fetuses with VSD and displayed the intact IVS in one fetus with transposition of the great arteries without VSD.

CONCLUSION

We describe live xPlane imaging, a simple method for the real-time assessment of the in-plane view of the IVS that has the potential to enhance the diagnostic accuracy of fetal cardiac examination.

Which ultrasound or biochemical markers are independent predictors of small-for-gestational age?

OBJECTIVES

To investigate which ultrasound or biochemical markers in both the first and the second trimesters are the best predictors for fetal growth and small-for-gestational age (SGA).

METHODS

This was a prospective study of 619 Chinese women with a singleton pregnancy. At 11 to 13 + 6 weeks, fetal crown-rump length (CRL), placental volume (PlaV), uterine artery pulsatility index (UtA-PI), and the maternal serum levels of pregnancy-associated plasma protein-A (PAPP-A) and free beta-human chorionic gonadotropin (beta-hCG) were measured. Fetal biparietal diameter, femur length, abdominal and head circumference, PlaV and UtA-PI were then measured at 18-22 weeks. All markers were transformed to gestational age-specific Z-scores or multiples of the median (MoM). Birth weights were also transformed to Z-scores using the individualized gestational age-related optimal weight based on a locally derived nomogram. The relationship between all markers and the customized birth weight were examined, and their predictive powers for SGA were examined by regression analysis.

RESULTS

Univariate analysis revealed that all markers except free beta-hCG correlated with birth weight Z-score. After multiple linear regression analysis, only PlaV, UtA-PI and CRL in the first trimester, and PlaV and UtA-PI in the second trimester, stood out as independent markers. Logistic regression analysis showed that PlaV was the only independent first-trimester predictor of SGA, and in the second trimester both PlaV and UtA-PI were independent predictors. The sensitivity of these first- and second-trimester markers in predicting SGA were 41% and 45%, respectively, at a false-positive rate of 20%. Combining them did not significantly improve prediction of SGA.

CONCLUSIONS

Among the various known ultrasound and biochemical markers, only the first-trimester PlaV and the second-trimester PlaV plus UtA-PI are independent predictors for SGA.

Suicides by jumping from iconic bridges in Hong Kong

BACKGROUND

Three bridges in Hong Kong have become iconic sites for suicide since their openings 11 years ago.

AIMS

This retrospective record-based study aimed to examine suicides by jumping from a group of three iconic bridges in Hong Kong, and to explore potential preventive strategies on these bridges to prevent future suicide.

METHODS

We examined the Coroner's files of 12 people who killed themselves by jumping from the bridges between 1997 and 2007. We also examined the Coroner's files of other suicides in 2003, and compared them with the bridge suicides.

RESULTS

The majority of the suicides were male, middle-age (40-59 years), married or cohabiting, not living alone, employed or self-employed, and in financial difficulty. None of these cases had a reported psychiatric diagnosis or psychiatric care history, and only one case had a history of suicidal attempt. Compared with other suicides in Hong Kong, the bridge jumpers were more likely to be younger, holding a job, indebted, free from a psychiatric and attempt history, and to leave a suicide note (p < .05). The bridge suicide cases in Hong Kong also appeared to be different from the profiles of bridge jumpers in other countries.

CONCLUSIONS

Erection of an effective safety barrier has been found to prevent bridge suicides in many countries. Given the different characteristics of bridge jumpers in Hong Kong and the technical difficulties, more innovative ways may be needed to prevent suicides by such means. Potential prevention measures are discussed and, hopefully, will better inform the future design and development of bridges of significance.

First-trimester fetal nasal bone length in an ethnic Chinese population

OBJECTIVES

To determine reference ranges of fetal nasal bone length (NBL) in a Chinese population and to assess the value of NBL measurement in screening for chromosomal defects in the first trimester.

METHODS

In this prospective study the fetal profile was examined and the fetal NBL and crown-rump length (CRL) were measured in Chinese women presenting with singleton pregnancies for first-trimester screening for aneuploidy between January 2004 and June 2007. Screening was performed on the basis of nuchal translucency (NT) measurement and maternal serum free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A levels.

RESULTS

NBL was measured in 7543 fetuses, of which 7517 were euploid. The best fit equation for median NBL in euploid fetuses in relation to CRL was: NBL (mm) = 0.4593 + (0.0186 x CRL(mm)). The NBL for gestational age (GA, in days) was given by the equation NBL(mm) = 0.2392 + (0.0027 x GA). There was no correlation between log(10)(NBL multiples of the median (MoM)) and log(10)(NT MoM) in unaffected pregnancies (r = - 0.009; P = 0.43). Only two of the 11 cases with trisomy 21 had an NBL outside the 5(th) or 95(th) centiles of the reference range for euploid fetuses.

CONCLUSION

Reference ranges for NBL in a Chinese population suitable for screening for aneuploidy between 11 and 13 + 6 weeks' gestation have been derived. The NBL in Chinese fetuses is similar to that of other ethnic groups. However, unlike the determination of presence vs. absence of the nasal bone, NBL measurement is unlikely to further improve screening for aneuploidy.

Volumetric (3D) imaging reduces inter- and intraobserver variation of fetal biometry measurements

OBJECTIVE

To compare the inter- and intraobserver variation of fetal biometric measurements utilizing two-dimensional (2D) and three-dimensional (3D) ultrasound imaging.

METHODS

This prospective study, utilizing three pairs of doctors trained in sonography, evaluated singleton pregnancies in the mid-trimester. Measurements of the biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL) were taken in duplicate by each doctor using 2D imaging and then again using 3D volume datasets. Each set of paired doctors evaluated 12 patients. Inter- and intraobserver variation were calculated as the SD of the difference between paired measurements performed by the doctor pairs and by the individual doctors, respectively. Bland-Altman plots were used to visually compare measurement bias and agreement by 2D and 3D methods.

RESULTS

Inter- and intraobserver variation for 2D and 3D ultrasound were small. The intraobserver variation of HC, AC and FL was significantly lower for 3D compared with 2D ultrasound. Interobserver variation was not significantly different when measured with 2D and 3D ultrasound, with the exception of FL, which was lower when measured with 3D ultrasound. The Bland-Altman plots showed that in 95% of the measurements, the percentage difference between 2D and 3D ultrasound techniques was within 5.3%, 4.6%, 9.6% and 9.6% for BPD, HC, AC and FL, respectively.

CONCLUSIONS

2D and 3D fetal biometric measurements are reproducible. The use of 3D ultrasound significantly reduces intraobserver variation for HC, AC and FL and reduces interobserver variation for FL.

Medians and correction factors for biochemical and ultrasound markers in Chinese women undergoing first-trimester screening for trisomy 21

OBJECTIVE

To establish normative values and distribution parameters of first-trimester maternal serum free beta-human chorionic gonadotropin (beta-hCG), pregnancy-associated plasma protein-A (PAPP-A) and fetal nuchal translucency (NT) thickness in Chinese women and to examine the effects of covariates on their levels.

METHODS

Maternal serum free beta-hCG, PAPP-A and fetal NT were measured in 9762 women presenting for first-trimester combined screening for Down syndrome at 11 to 14 weeks of gestation. Individuals' markers were converted to multiples of the median (MoM) using expected medians estimated by performing a weighted regression analysis. Multivariate regression analysis was performed to assess the influence of maternal weight, parity, ethnicity, chorionicity in twin pregnancies, smoking, insulin-dependent diabetes and mode of conception on individual marker MoM levels.

RESULTS

Both free beta-hCG and PAPP-A median values demonstrated an exponential relationship with gestational age in days. Multivariate regression analysis indicated that free beta-hCG MoM was statistically significantly dependent on maternal weight (P < 0.0001) and chorionicity in twin pregnancy (both monochorionic and dichorionic P < 0.0001), that PAPP-A MoM was dependent on maternal weight (P < 0.0001), parity (P < 0.0001), chorionicity in twin pregnancy (both monochorionic and dichorionic P < 0.0001) and mode of conception (P = 0.002), and that fetal NT-MoM was dependent on maternal weight (P = 0.0006) and mode of conception (P = 0.012).

CONCLUSION

Normative values have been generated to allow conversion of NT, free beta-hCG and PAPP-A to their MoM equivalents and correction factors have been determined to adjust for maternal and pregnancy characteristics for use in ethnic Chinese women undergoing first-trimester screening for aneuploidy.

Fetal crown-rump length and estimation of gestational age in an ethnic Chinese population

OBJECTIVES

To develop a sonographic dating formula based on fetal crown-rump length (CRL) in a Hong Kong Chinese population, quantify its systematic prediction error and compare its performance with established dating formulae.

METHODS

This was a prospective observational study of women with a spontaneously conceived singleton pregnancy and a regular menstrual cycle in the preceding 12-month period. Ultrasound examinations were performed at gestational ages ranging from 6 to 15 + 6 weeks according to menstrual dates. The CRL of each fetus was measured three times, the mean of which was used to derive the best-fit fractional polynomial regression model for estimation of gestational age in relation to CRL. For each fetus, the menstrual age was compared to the gestational age calculated using three established dating formulae based on CRL measurement. The mean of the differences between estimated and menstrual age was calculated for each formula.

RESULTS

Of the 394 subjects recruited one was excluded as the pregnancy resulted in intrauterine demise. The best-fit equation for the sonographic estimate of gestational age (GA, in days) from CRL (in mm) was GA = 26.643 + 7.822 x CRL(1/2)(R(2) = 0.96). The mean difference between menstrual age and the predicted gestational age was 0.22 days (95% CI, - 0.14 to 0.56), which was lower than that of the three established CRL dating formulae.

CONCLUSION

We have derived a formula suitable for the dating of naturally conceived pregnancies between 6 and 15 weeks of gestation that has no systematic prediction error (the 95% CI of mean difference between predicted and menstrual age included zero), comparing favorably with established CRL dating formulae.

How true is a 'true' midsagittal section?

OBJECTIVES

To study the deviation of presumed midsagittal sections of the fetal head from the true image plane, to compare whether certification (by The Fetal Medicine Foundation (FMF), UK) has an effect on the degree of this deviation, and to investigate the impact of imperfect midsagittal sections on nuchal translucency thickness (NT) measurement.

METHODS

Eight sonographers, four of them FMF-certified (Group A) and the other four not (Group B), were asked to obtain image sections which they believed to represent true midsagittal sections of the fetal head and neck in five patients each. Three-dimensional volume datasets were acquired for subsequent analysis. The angle between the falx cerebri and the vertical axis was measured and the effect of this angle on NT measurement was assessed.

RESULTS

The mean angle of deviation was significantly lower among those who were FMF-certified (5.7 degrees vs. 14.7 degrees, P < 0.001). The 1.8% underestimation of NT by Group A was not statistically significant (P = 0.76), while in Group B the NT could not be measured when the angle of deviation was 14.7 degrees.

CONCLUSIONS

FMF-certified operators obtain a better midsagittal section compared with non-certified operators. The minor deviation from the true midsagittal section by certified operators has no significant effect on the value of NT measurement. This study could provide a model for operator training and auditing.

Customized birth weight: coefficients and validation of models in a UK population

OBJECTIVES

To produce a customized birth weight model in a UK population.

METHODS

This was a population-based, multiethnic, retrospective cohort study of 42,583 women with uncomplicated singleton pregnancies resulting in a live birth at 37-42 weeks of gestation between 1997 and 2005. Multivariate analysis was undertaken and a double cross-over approach was employed to validate the models estimating customized birth weight.

RESULTS

Coefficients confirmed the findings of previous studies, indicating that birth weight was strongly influenced by maternal ethnicity, age, parity, body mass index, smoking, fetal gender and gestational age at delivery.

CONCLUSIONS

We have derived models to determine customized or predicted birth weight in a UK population that are both robust and reproducible.

Side-effect and vital sign profile of nifedipine as a tocolytic for preterm labour

OBJECTIVE

To examine the side-effect and vital sign profile of nifedipine used as a tocolytic.

DESIGN

Retrospective audit.

SETTING

Tertiary care university hospital, Hong Kong.

PATIENTS

Women presenting with preterm labour (before 34 weeks of gestation) between March 2001 and September 2004.

MAIN OUTCOME MEASURES

Maternal heart rate, blood pressure, and foetal heart rate were monitored regularly. A four-point Likert scale multiple-choice questionnaire was used to assess the perceived degree of flushing, headache, nausea, dizziness, and shortness of breath. All assessments were performed at predefined intervals from the onset of treatment. Repeated measures analysis of variance was performed to identify any time-dependent association with nifedipine treatment.

RESULTS

In all, 212 episodes of preterm labour were treated with nifedipine in 203 women. In 120 episodes, preterm labour was suppressed for more than 48 hours. Treatment was discontinued in three women because of profound hypotension (<90/60 mm Hg), and in one because of severe flushing. Only one patient developed maternal tachycardia (>or=140 beats per minute), and in two foetal tachycardia (>or=180 beats per minute) was encountered. Moderate headache was experienced in nine women, flushing in nine, dizziness in four, nausea in three, and shortness of breath in one. Repeated measures analysis of variance with time of measurement revealed a significant reduction in maternal blood pressure and increase in maternal heart rate that plateaued after 1 hour of therapy. The foetal heart rate returned to baseline values 3 hours after commencing therapy.

CONCLUSION

In general, use of nifedipine as the first-line tocolytic was safe. However, severe maternal hypotension can occur and close monitoring of vital signs is warranted.

Umbilical cord ulceration causing foetal haemorrhage and stillbirth

We report a case of umbilical cord ulceration associated with obstruction of the duodeno-jejunal junction by a peritoneal band. Umbilical cord ulceration is a rare condition; a literature review identified a total of 17 cases only. In all cases, the ulceration was associated with congenital intestinal obstruction. Cord ulceration usually presents as sudden foetal deterioration due to foetal haemorrhage. This condition is associated with high perinatal mortality and morbidity. The causes of this condition are still unknown, and prenatal diagnosis is difficult. Awareness of the possible association between umbilical cord ulceration and intestinal obstruction, and of the need to deliver such pregnancies immediately when an abnormal foetal heart rate pattern develops might be the only means of preventing intrauterine death and improving neonatal outcomes.

Fetal biometry in ethnic Chinese: biparietal diameter, head circumference, abdominal circumference and femur length

OBJECTIVES

To construct new reference charts and equations for fetal biometry in the Hong Kong ethnic Chinese population, and to compare them with existing references from different populations.

METHODS

This was a prospective observational study involving 709 women with singleton pregnancies and confirmed gestational age. For the purposes of this study, each woman was scanned once only, between 12 and 40 completed weeks of gestation, and the following fetal biometric measurements were recorded: biparietal diameter, head circumference, abdominal circumference and femur length. For each measurement, regression models were fitted to estimate the mean and SD at each gestational age. For comparison, the fetal biometric measurements of other populations at each gestation were expressed as Z-scores calculated with our reference equations. Results were presented graphically across the different gestational ages to allow visual comparison.

RESULTS

New charts and reference equations are reported in this Hong Kong Chinese population for fetal outer-inner and outer-outer biparietal diameter, head circumference, abdominal circumference and femur length. Equations for dating of pregnancy are presented. Our charts were very similar to those of the Singaporean population for most parameters. The main difference in our fetal biometric measurements compared with those of the UK and French populations was in FL.

CONCLUSIONS

Our new set of reference centiles for fetal biometric measurements and equations for dating of pregnancy in a Hong Kong Chinese population are ready for clinical use and research in appropriate ethnic Chinese groups.

Rapid aneuploidy testing (knowing less) versus traditional karyotyping (knowing more) for advanced maternal age: what would be missed, who should decide?

OBJECTIVES

The application of rapid aneuploidy testing as a stand-alone approach in prenatal diagnosis is much debated. The major criticism of this targeted approach is that it will not detect other chromosomal abnormalities that will be picked up by traditional karyotyping. This study aimed to study the nature of such chromosomal abnormalities and whether parents would choose to terminate affected pregnancies.

DESIGN

Retrospective study on a cytogenetic database.

SETTING

Eight public hospitals in Hong Kong.

PARTICIPANTS

The karyotype results of 19 517 amniotic fluid cultures performed for advanced maternal age (>or=35 years) from 1997 to 2002 were classified according to whether they were detectable by rapid aneuploidy testing. The outcomes of pregnancies with abnormal karyotypes were reviewed from patient records.

RESULTS

In all, 333 (1.7%) amniotic fluid cultures yielded abnormal karyotypes; 175 (52.6%) of these were detected by rapid aneuploidy testing, and included trisomy 21 (n=94, 28.2%), trisomy 18 or 13 (n=21, 6.3%), and sex chromosome abnormalities (n=60, 18.0%). The other 158 (47.4%) chromosomal abnormalities were not detectable by rapid aneuploidy testing, of which 63 (18.9%) were regarded to be of potential clinical significance and 95 (28.5%) of no clinical significance. Pregnancy outcomes in 327/333 (98.2%) of these patients were retrieved. In total, 143 (42.9%) of these pregnancies were terminated: 93/94 (98.9%) for trisomy 21, 20/21 (95.2%) for trisomy 18 or 13, 19/60 (31.7%) for sex chromosome abnormalities, and 11/63 (17.5%) for other chromosomal abnormalities with potential clinical significance. There were no terminations in the 95 pregnancies in which karyotyping results were regarded to be of no clinical significance.

CONCLUSIONS

'Knowing less' by the rapid aneuploidy stand-alone testing could miss about half of all chromosomal abnormalities detectable by amniocentesis performed for advanced maternal age. Findings from two fifths of the latter were of potential clinical significance, and the parents chose to terminate one out of six of the corresponding pregnancies. If both techniques are available, parents could have enhanced autonomy to choose.

Prediction of birth weight by fetal crown-rump length and maternal serum levels of pregnancy-associated plasma protein-A in the first trimester

OBJECTIVE

To determine whether the first trimester crown-rump length (CRL), maternal serum levels of pregnancy-associated plasma protein A (PAPP-A) and free beta-human chorionic gonadotropin (fbeta-hCG) are independent predictors of birth weight.

METHODS

This was an observational study over 1.5 years in Chinese patients who underwent first-trimester combined screening for Down syndrome in a University fetal medicine unit. After excluding cases with multiple pregnancies, congenital malformations and in-utero deaths, the relationship between fetal CRL (expressed as standardized Z-score (Z-CRL)), maternal PAPP-A and fbeta-hCG levels (expressed as log(10) of multiples of the median) and birth weight (Z-BW) were analyzed by Pearson's correlation test followed by multiple regression to check for their independency. The predictive power of the independent predictors for small-for-gestational age (SGA, defined as birth weight < 10(th) centile) was then assessed using receiver-operating characteristics (ROC) curves, and the likelihood ratios were derived.

RESULTS

A total of 2760 cases were included. Z-CRL, log(10) PAPP-A(MoM), and log(10) fbeta-hCG were positively correlated with Z-BW (P < 0.0001), but only Z-CRL and log(10) PAPP-A(MoM) were independent predictors (P < 0.0001). The areas under the ROC curves of PAPP-A(MoM) and Z-CRL were 0.608 and 0.593, respectively (P < 0.0001). Likelihood ratios increased with decreasing PAPP-A(MoM) and Z-CRL, but were around 1 when the markers were at or above the mean.

CONCLUSION

First-trimester CRL and PAPP-A are independent factors that influence final birth weight. The lower the PAPP-A and the smaller the CRL, the higher the risk of a fetus becoming SGA. However, their predictive powers are not sufficiently good for them to be used alone for SGA screening.

Foetal intracranial teratoma: choosing the best time and mode of delivery

We present a case of foetal intracranial teratoma diagnosed at 28 weeks of gestation after prior normal sonographic examinations. A multidisciplinary team, involving obstetricians, neonatologists, and neurosurgeons, suggested management. The foetus was delivered by lower segment caesarean section at 30 weeks of gestation but the neonate succumbed 3 days after delivery, 1 hour after the withdrawal of active treatment. Issues governing the timing and mode of delivery, together with the role of cephalocentesis in the management of this condition, are discussed.