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.