Chin Peng Lee

Early ultrasound prediction of pregnancies affected by homozygous α-thalassaemia-1

Homozygous α‐thalassaemia‐1 is conventionally diagnosed by invasive testing on all at‐risk pregnancies. We evaluated the diagnostic efficacy of non‐invasive abdominal ultrasonographic cardiothoracic ratio measurement in 62 pregnancies at 13–14 weeks and 75 pregnancies at 17–18 weeks. This performed better than placental thickness measurement. Using a cardiothoracic ratio cut‐off level of ≥0·5, 75 per cent of affected pregnancies were detected at 13–14 weeks and all cases were detected at 17–18 weeks. False‐positive rates were 7 and 8 per cent, respectively. There was no false‐positive diagnosis if the cardiothoracic ratio was ≥0·53. With this approach, invasive procedures can be selectively performed and fewer pregnancies will be lost unnecessarily. The reduction in medical expenses is likely to be substantial.

Prenatal ultrasonographic prediction of homozygous type 1 α-thalassemia at 12 to 13 weeks of gestation☆☆☆★

We determined the feasibility of prenatal prediction of type 1 homozygous alpha-thalassemia at 12 to 13 weeks of gestation by either abdominal or vaginal (or both) ultrasonographic examination to measure the fetal cardiothoracic ratio in 135 at-risk pregnancies. Forty-three fetuses were affected by homozygous type 1 alpha-thalassemia. The mean cardiothoracic ratio was significantly larger than that of the unaffected fetuses (0.54 vs 0.45, P <.0005), with no overlap between the 2 groups. A cardiothoracic ratio cutoff point of >/=0.5 was 100% sensitive and specific for disease.

Placental weight to birthweight ratio is increased in mild gestational glucose intolerance

To determine if the placental weight to birthweight ratio (placental ratio) is increased in pregnancies complicated by diet-treated gestational impaired glucose tolerance (IGT) and diabetic (GDM) pregnancies, a retrospective case control study was performed on 478 singleton IGT/GDM pregnancies delivered in 1994 and compared with a control group that consisted of the next case with normal OGTT performed on the same day as each index case. The placental weight and ratio, and the placental ratio alone, were found to be significantly increased in the IGT and GDM groups respectively compared with the control group. Significant correlation was demonstrated between the placental ratio with OGTT 2-h value and maternal body mass index. Multiple regression analysis indicated that the OGTT 2-h value was the significant determinant for placental ratio. Our results showed that increased placental size and ratio were found in IGT/GDM pregnancies that required diet treatment only, and this increase was related to the degree of glucose intolerance as shown in the OGTT 2-h value.

Comparison of nuchal and detailed morphology ultrasound examinations in early pregnancy for fetal structural abnormality screening: a randomized controlled trial

To compare the effectiveness of a nuchal scan at 10 to 14 + 6 weeks and a detailed morphology scan at 12 to 14 + 6 weeks in screening for fetal structural abnormalities.

Fetal cerebral doppler studies as a predictor of perinatal outcome and subsequent neurologic handicap

Objective To study the use of middle cerebral arterial Doppler findings in a group of high-risk fetuses as a predictor of adverse perinatal outcome, including subsequent neurologic handicap. Methods A group of very high-risk fetuses was recruited over a 2-year period for study. Weekly fetal biometries and Doppler studies of the umbilical artery and middle cerebral arteries were carried out until delivery. Main outcome indices analyzed included birth weight ratio (ratio of observed birth weight to mean birth weight for gestation), days of ventilator requirement, neonatal intracranial hemorrhage or periventricular leukomalacia, necrotizing enterocolitis, and follow-up data on major neurologic handicap and death. Results Seventy-four patients were recruited. One hundred thirty-four sets of examinations were made and prospective follow-up data were available for up to 2 years. The ratio of the umbilical and middle cerebral arterial resistance index was found to be inversely proportional to the birth weight ratio. Fetuses who had a high prenatal umbilical-cerebral Doppler ratio had significantly lower birth weight ratios than those with normal findings (0.72 versus 0.92; P < .001). The ratio was a more sensitive marker for growth restriction (sensitivity 78%) than conventional fetal biometry and umbilical arterial systolic-diastolic ratio. However, fetuses with high ratios did not have higher incidences of perinatal complications or subsequent neurologic handicap. Conclusion Prenatal cerebral vasodilation is a sensitive marker for growth restriction and it seems to be a physiologic response to hypoxia. Fetuses with intrauterine cerebral vasodilation do not have increased risk for subsequent gross neurologic damage.

Three‐dimensional extended imaging: a new display modality for three‐dimensional ultrasound examination

To describe Three‐Dimensional eXtended Imaging (3DXI)™ as a new display modality for three‐dimensional (3D) ultrasound examination of the fetus.

Second-trimester maternal serum alpha-fetoprotein and human chorionic gonadotrophin screening for Down's syndrome in Hong Kong

Second‐trimester maternal serum screening for fetal Downs syndrome is well established in many Western countries. Its usefulness and acceptability is unknown in the Asian countries. Between June 1994 and December 1996, we offered second‐trimester serum AFP and hCG screening to pregnant women in Hong Kong who were less than 35 years old and without other risk factors for chromosomal abnormalities. Each woman was assigned a risk of having a Downs syndrome term pregnancy by using a computer software program that took into account her age, weight, AFP and hCG MOMs. All those with a risk of one in 250 or greater were designated screen‐positive, subject to the revision of gestation by ultrasound examination. 9177 women with singleton pregnancies (93 per cent were Chinese) were screened. The uptake of screening was 75 per cent. 281 women (three per cent) were initially classified to be screen‐positive. After revision of the gestation by ultrasound examination, 183 women (two per cent) were ‘true’ screen‐positive and 164 (90 per cent) accepted the offer of amniocentesis. Eight of these pregnancies were affected by Downs syndrome and all the women elected pregnancy termination. The odds of being affected, given a positive screening result, were one in 23. Six Downs syndrome pregnancies were missed by the screening programme. The detection rate was 57 per cent. The study showed that second‐trimester serum screening for fetal Downs syndrome was feasible and acceptable in the Hong Kong population.

A pilot‐randomized comparison of sublingual misoprostol with syntometrine on the blood loss in third stage of labor

Background.  To compare sublingual misoprostol with intravenous syntometrine use during third stage of labor by measuring the blood loss.

Placental volume measured by three‐dimensional ultrasound in the prediction of fetal α0‐thalassemia: a preliminary report

To evaluate the use of placental volume measured by three‐dimensional (3D) ultrasound in predicting fetal homozygous α0‐thalassemia (Hb‐Barts disease).

Whole-genome array CGH evaluation for replacing prenatal karyotyping in Hong Kong.

Objective To evaluate the effectiveness of whole-genome array comparative genomic hybridization (aCGH) in prenatal diagnosis in Hong Kong. Methods Array CGH was performed on 220 samples recruited prospectively as the first-tier test study. In addition 150 prenatal samples with abnormal fetal ultrasound findings found to have normal karyotypes were analyzed as a ‘further-test’ study using NimbleGen CGX-135K oligonucleotide arrays. Results Array CGH findings were concordant with conventional cytogenetic results with the exception of one case of triploidy. It was found in the first-tier test study that aCGH detected 20% (44/220) clinically significant copy number variants (CNV), of which 21 were common aneuploidies and 23 had other chromosomal imbalances. There were 3.2% (7/220) samples with CNVs detected by aCGH but not by conventional cytogenetics. In the ‘further-test’ study, the additional diagnostic yield of detecting chromosome imbalance was 6% (9/150). The overall detection for CNVs of unclear clinical significance was 2.7% (10/370) with 0.9% found to be de novo. Eleven loci of common CNVs were found in the local population. Conclusion Whole-genome aCGH offered a higher resolution diagnostic capacity than conventional karyotyping for prenatal diagnosis either as a first-tier test or as a ‘further-test’ for pregnancies with fetal ultrasound anomalies. We propose replacing conventional cytogenetics with aCGH for all pregnancies undergoing invasive diagnostic procedures after excluding common aneuploidies and triploidies by quantitative fluorescent PCR. Conventional cytogenetics can be reserved for visualization of clinically significant CNVs.