Foetal peak systolic velocity in the middle cerebral artery: an Asian reference range.

INTRODUCTION: The aim of this study was to establish reference values of peak systolic blood flow velocity measurement in the foetal middle cerebral artery (MCA-PSV) in the local Asian obstetric population and to compare our reference ranges with those of previously-published studies. METHODS: 329 normal pregnant women attending the outpatient antenatal clinics of the Department of Obstetrics and Gynaecology in the Singapore General Hospital underwent Doppler ultrasonography at least once between 16 and 40 weeks' gestation. The blood flow velocity recordings from the foetal middle cerebral artery were obtained. New reference ranges were constructed by regressing each parameter on gestational age. RESULTS: New reference ranges for foetal middle cerebral artery with gestation were constructed for an Asian population. Our reference curves were compared with that of a previously-constructed one. CONCLUSION: MCA-PSV increases with advancing gestational age. There appear to be differences between Asian and non-Asian reference ranges for MCA-PSV.

Pattern of Turner syndrome in Singapore (1999-2004).

INTRODUCTION: Turner syndrome is the most common sex chromosomal abnormality in female foetuses, and is associated with a high proportion of cardiac anomalies. The aim of this study was to look at the incidence, demographical data and epidemiological pattern of Turner syndrome in Singapore from 1999 to 2004 and to examine the birth defects associated with this condition, specifically with reference to cardiac defects. METHODS: Data on Turner syndrome cases born in 1999-2004 were retrieved from the National Birth Defects Registry (NBDR) and analysed. Data on congenital cardiac defect cases notified to the NBDR in the same time period were also retrieved and compared with the Turner syndrome cases. RESULTS: There were a total of 101 cases of Turner syndrome in the six-year period from 1999-2004, yielding an overall incidence of 0.85 per 1,000 female live births, or one in 1,180 female live births. The incidence was lowest among Indians (0.38 per 1,000) compared to Malays (0.72 per 1,000) and Chinese (0.90 per 1,000). 75 cases (74.3 percent) had the 45,X karyotype, while the other 26 cases (25.7 percent) were mosaics. The mean maternal age for 45,X was lower (32.2 years, range 22-42) compared to mosaics (34.5 years, range 27-40). 19.8 percent (20/101) were live births, 38.6 percent (39/101) were terminated pregnancies and 41.6 percent (42/101) were spontaneous miscarriages. 13.9 percent of Turner syndrome babies had cardiac defects compared to 1.2 percent in the general population (p-value is less than 0.0001). Major cardiac defects found among Turner syndrome babies compared to the general population included the coarctation of the aorta (5.9 percent compared to 0.03 percent, p-value is less than 0.0001), atrial septal defects (3.0 percent compared to 0.6 percent, p-value is 0.006), a hypoplastic left heart (2.0 percent compared to 0.05 percent, p-value is less than 0.0001), aortic hypoplasia (3.0 percent compared to 0.01 percent, p-value is less than 0.0001) and dextrocardia (1.0 percent compared to 0.02 percent, p-value is 0.0002). CONCLUSION: Cardiac defects, particularly left-sided ones, are significantly more common among Turner syndrome foetuses. The true incidence of this syndrome is likely to be higher than that quoted in this study, and can only be solved when a complete screening of an entire population has been performed.

Cleft deformities in Singapore: a population-based series 1993-2002.

INTRODUCTION: Cleft deformities, though non-lethal, receive much attention from parents and doctors alike because of their obvious physical disfigurement, social stigma and associated feeding and vocal articulation problems. There is also an association with chromosomal defects for certain cleft deformities. The aim of this study is to examine the incidence, demographic data and epidemiological trend of this condition over a ten-year period, and to compare our data with other local studies, as well as to examine the chromosomal defects associated with this condition. METHODS: Data of cleft deformity cases born during the period 1993-2002 was retrieved from the National Birth Defects Registry and analysed. RESULTS: There were a total of 859 cases of cleft deformities in the ten-year period 1993-2002, giving an overall incidence of 1.87 per 1,000 live births, with an increasing trend noted. Incidence was highest among the Chinese and lowest among the Indians. There were more males with cleft deformities compared with females. The risk of aneuploidy rose by about ten-fold in syndromic cleft cases, compared to non-syndromic cleft cases. There were two cases of Trisomy 21 in the non-syndromic cleft lip and palate group, giving an incidence of 1:133. CONCLUSION: The race-specific and gender-specific differences in cleft incidence suggest genetic and environmental factors which warrant further studies. The increased risk of aneuploidy among syndromic clefts, as well as the finding of Trisomy 21 in non-syndromic cleft lip and palate cases suggest a need for karyotyping in these two groups of antenatally-diagnosed cleft deformities.

22q11.2 deletion syndrome in Singapore (2000-2003): a case for active ascertainment.

INTRODUCTION: The 22q11 deletion syndrome (22q11DS) is associated with many congenital structural anomalies, notably cardiac defects (conotruncal anomalies) and velopharyngeal insufficiency, as well as neurodevelopmental and psychiatric findings in later life. Recent studies have tried to ascertain the true population incidence of this condition. However, this is difficult due to possible under-ascertainment from incomplete genetic testing in possible cases. The aim of this study is to investigate the local incidence and association of this deletion syndrome with other congenital structural anomalies, with emphasis on cardiac defects. METHODS: Data of 22q11 deletion cases born in 2000-2003 were retrieved from the Singapore National Birth Defects Registry (NBDR) and analysed. Data of congenital cardiac defect cases notified to NBDR in the same period were also retrieved and compared with the deletion cases. RESULTS: There were a total of 17 cases of 22q11DS in the four-year period 2000-2003, giving an overall incidence of 1.02 per 10,000 live-births or one in 9,804 births. 94 percent (16/17 cases) were associated with other structural anomalies, and of these, 68.8 percent (11/16 cases) had single system anomalies. Cardiac anomalies were the most common (100 percent). The deletion contributed to 0.86 percent (one in 116 cases) of all cardiac defects born during the same period. A higher contribution of this deletion was noted for interrupted aortic arch (10 percent), pulmonary atresia (12.7 percent) and truncus arteriosus (11.1 percent). CONCLUSION: In view of the high proportion of this deletion among certain cardiac defects, genetic testing should be made available to investigate the true burden and contribution of this deletion. As more genetic testing is done for this deletion, we are likely to see an increase in incidence, reflecting the true prevalence of this condition.

Anencephaly in Singapore: a ten-year series 1993-2002.

INTRODUCTION: Anencephaly is a neural tube defect that is incompatible with life. Previous studies have suggested that there is a racial predilection for this condition. However, local studies have not shown a statistical difference between the races. The aim of this study is to examine the incidence and the demographical trend of this condition over a ten-year period. METHODS: Data of patients with anencephaly born from 1993 to 2002 were retrieved from the National Birth Defect Registry and analysed. RESULTS: There were a total of 267 cases of anencephaly in the ten-year period from 1993 to 2002, giving an overall incidence of 0.58 per 1,000 livebirths, with a decreasing trend noted. The incidence was highest among the Malay population, compared with the Chinese population (p-value equals 0.03) and other races. Abortion rates have also increased over the years, causing a reduction in livebirth rates for this condition. CONCLUSION: The overall incidence and birth incidence of anencephaly has seen a decreasing trend over the last ten years, with the latter being contributed significantly by early termination. More studies should be done to ascertain if improved folate supplementation has contributed to the drop in overall incidence. The incidence in the Malay population is significantly higher than other races and this phenomenon should be further examined.

The amniotic sheet: a truly benign condition?

OBJECTIVE: Amniotic sheets are the result of uterine synechiae that have been encompassed by the expanding chorion and amnion. Radiologically they are seen as 'shelves' in the amniotic cavity. The benign nature of such amniotic sheets has been documented in many case series in the literature. The objective of this study was to determine the characteristics (if any) of amniotic sheets that predict fetal outcome. METHODS: Between January 2001 and December 2002, detailed scans were performed in 30 476 singleton pregnancies at 18-32 weeks' gestation. Of these, 44 cases of amniotic sheets were detected. The characteristics studied were site of amniotic sheet and whether the amniotic sheet was complete (i.e. no free edge seen on ultrasound) or incomplete (i.e. presence of free edge seen on ultrasound). The primary fetal outcome studied was stillbirth. RESULTS: The incidence of amniotic sheets was 0.14%. Two were complete and 42 were incomplete. Of the 38 cases with known outcomes there were two intrauterine deaths. There was no association between fetal outcome and the uterine location of the amniotic sheet (i.e. upper two-thirds vs. lower third, P = 0.5). There was, however, an association between the completeness of the amniotic sheets and intrauterine death (P = 0.002). Both instances of intrauterine death occurred in the two cases with complete amniotic sheets. Postmortem examination suggested that cord accidents were the cause of intrauterine death in both cases. CONCLUSIONS: This study supports the view that incomplete amniotic sheets are benign. It also suggests for the first time that complete amniotic sheets may be associated with intrauterine death.