OBJECTIVE: Analyze indications and type of prenatal diagnostic procedures performed.
METHOD: This retrospective audit was conducted at a dedicated fetal medicine center in Petaling Jaya. All invasive prenatal diagnosis procedures performed from 2003 up until 2010 (amniocentesis, chorionic villous sampling and fetal blood sampling) were analyzed.
RESULT: A total of 1560 invasive prenatal diagnostic procedures were performed during the 8 year period. Advanced maternal age is the leading indication for invasive prenatal diagnostic procedures followed by fetal abnormalities. The fetal loss rate was 0.2% for amniocentesis and 1.2% for CVS.
CONCLUSION: Advanced maternal age is the leading indication for invasive prenatal diagnostic procedures at this centre but is on a declining trend. The fetal loss rates are comparable to auditable standards set by professional bodies, in this case, the Royal College of Obstetricians & Gynecologists of London.
DNA analysis for the diagnosis of beta-thalassaemia is a relatively new technique in Malaysia. This, combined with chorionic villus sampling, has enabled us to offer prenatal diagnosis in the first trimester for this common condition. To the best of our knowledge, this has not hitherto been reported in Malaysia.
Smaller family size and advancing parental age have increased the demand for prenatal diagnosis.
Prenatal cytogenetic diagnoses currently used, such as amniocentesis and chorionic villus
sampling, are usually not preferred by the expectant couples due to the risk imposed on the mother and child. High false positive rates (5%) of current non-invasive screening methods, such as serum analysts or ultrasound, cause a large number of unnecessary invasive practices to be performed, which apart from the associated risk, place considerable psychological distress on the couples
involved (Wald et al., 1999). (Copied from article).
A nonconsanguineous asymptomatic couple, were identified as carriers of factor VII (FVII) deficiency when two of their newborn children died of massive intracranial hemorrhage secondary to severe congenital FVII deficiency. Complete sequence analysis of the factor VII (F7) gene in this couple indicated that the mother was heterozygous for an A to G transition at position -2 of the exon 5 acceptor splice site, and the father was heterozygous for a G to T transversion at position +1 of the exon 6 donor splice site. This information allowed us to exclude a compound heterozygous deficiency state in a subsequent pregnancy using PCR/direct sequencing of the F7 gene using DNA obtained from chorionic villi at 10 weeks' gestation. Our experience with the family reported here further supports the conclusion that mutation-specific detection is reliable in the prenatal exclusion of severe bleeding disorders.
A 25-month-old boy with beta-thalassaemia major was presented with an opportunity for umbilical cord blood transplantation when his unborn sibling was diagnosed in utero to be a beta-thalassaemia carrier and also human leucocyte antigen compatible. A barely adequate amount of cord blood was collected at the birth of his sibling and infused into the patient after appropriate chemo-conditioning. Engraftment occurred without major complications. The subject is now alive and well 9 months post-transplant, thus marking our first success in umbilical cord blood transplantation.
Haemoglobin Bart's hydrops foetalis syndrome (--SEA/--SEA) is not compatible with life and contributes to a majority of the hydropic foetuses in the Malaysian Chinese alpha-thalassaemia carriers who possess the 2-alpha-gene deletion in cis (--SEA/alphaalpha). A duplex-PCR which simultaneously amplifies a normal 136 bp sequence between the psialpha-alpha2-globin genes and a 730 bp Southeast Asian deletion-specific sequence (--SEA) between the psialpha2-theta1-globin genes was established. The duplex-PCR which detects the --SEA deletion in both chromosomes serves as a rapid and cost-effective confirmatory test in the antenatal diagnosis of Haemoglobin Bart's hydrops foetalis syndrome in Malaysia. In addition, the duplex-PCR is simple to perform as both the normal and deletion-specific alpha-globin gene sequences are amplified in the same PCR reaction.
Beta-thalassemia is the most-common genetic disorder of hemoglobin synthesis in Malaysia, and about 4.5% of the population are heterozygous carriers of the disorder. Prenatal diagnosis was performed for 96 couples using the Amplification Refractory Mutation System and Gap-Polymerase Chain Reaction. We identified 17 beta-globin defects-initiation codon for translation (T-G), -29 (A-G), -28 (A-G), CAP +1 (A-C), CD 8/9 (+G), CD 15 (G-A), CD 17 (A-T), CD 19 (A-G), Hb E (G-A), IVS1-1 (G-T), IVS1-5 (G-C), CD 41/42 (-CTTT), CD 71-72 (+A), IVS2-654 (CT), poly A(A-G), 100-kb Ggamma(Agammadeltabeta) degrees and 45-kb Filipino deletions. The 192 beta-alleles studied comprised Chinese (151 patients), Malay (21), Orang Asli from East Malaysia (15), Filipino (1), Indian (1), Indonesian Chinese (2), and Thai (1). In the Chinese, 2 beta-globin defects at CD 41/42 and IVS2-654 were responsible for 74% of beta-thalassemia. beta-mutations at CD 19, IVS1-1 (G-T), IVS1-5, poly A, and hemoglobin E caused 76% of the hemoglobin disorders in the Malays. The Filipino 45-kb deletion caused 73.3% of bthalassemia in the Orang Asli. Using genomic sequencing, the rare Chinese beta-mutation at CD 43 (G-T) was confirmed in 2 Chinese, and the Mediterranean mutation IVS1-1 (G-A) was observed in a Malay beta-thalassemia carrier. The beta-globin mutations confirmed in this prenatal diagnosis study were heterogenous and 65 (68%) couples showed a different globin defect from each other. The use of specific molecular protocols has allowed rapid and successful prenatal diagnosis of beta-thalassemia in Malaysia.