Invasive & non-invasive approaches for prenatal diagnosis of haemoglobinopathies: Experiences from India.

The thalassaemias and sickle cell disease are the commonest monogenic disorders in India. There are an estimated 7500 - 12,000 babies with β-thalassaemia major born every year in the country. While the overall prevalence of carriers in different States varies from 1.5 to 4 per cent, recent work has shown considerable variations in frequencies even within States. Thus, micromapping would help to determine the true burden of the disease. Although screening in antenatal clinics is being done at many centres, only 15-20 per cent of pregnant women register in antenatal clinics in public hospitals in the first trimester of pregnancy. There are only a handful of centres in major cities in this vast country where prenatal diagnosis is done. There is considerable molecular heterogeneity with 64 mutations identified, of which 6 to 7 common mutations account for 80-90 per cent of mutant alleles. First trimester foetal diagnosis is done by chorionic villus sampling (CVS) and DNA analysis using reverse dot blot hybridization, amplification refractory mutation system (ARMS) and DNA sequencing. Second trimester diagnosis is done by cordocentesis and foetal blood analysis on HPLC at a few centres. Our experience on prenatal diagnosis of haemoglobinopathies in 2221 pregnancies has shown that >90 per cent of couples were referred for prenatal diagnosis of β-thalassaemia after having one or more affected children while about 35 per cent of couples were referred for prenatal diagnosis of sickle cell disorders prospectively. There is a clear need for more data from India on non-invasive approaches for prenatal diagnosis.

Evaluation of early complications of chorionic villus sampling

Chorionic villus sampling [CVS] is a minor surgical procedure performed with the purpose of prenatal diagnosis of congenital foetal anomalies. There are concerns regarding the safety and success of the procedure because of the possible complications associated with it. Since its introduction in Nigeria, the first in sub-Saharan Africa, several cases has been performed but no review of the complications has been undertaken. The purpose of the study was to evaluate the early complications of chorionic villus sampling as a basis for an improved performance of the procedure. The clinical records of all the CVS performed during a two year period [1[st] January, 2002-31[st] December,2003] were analyzed retrospectively. The biodata as well as the various clinical characteristics of the patients and the complications associated with the procedure were reviewed. The frequency and distribution of these complications by the route of sampling and location of the placenta were also analyzed. One hundred and forty women were counseled, out of which 130 [92.9%] underwent the procedure. Four [3.1%] each, could not be done due to operational difficulty or failure of the patients to turn up for the procedure. Transabdominal route [50.8%] with placenta located in the uterine body anteriorly [53.1%] was the commonest finding. Complications were recorded in 47 cases [36.2] of these complications the most frequent was bleeding [65.9%] and was associated mostly with placenta located in the uterus body posteriorly and a transcervical route of sampling. Abortion, the 2[nd] commonest complication [29.8%] occurred slightly more in the transcervical than the transabdominal route. Iatrogenic rupture of membrane and abdominal pains or discomfort was associated with only 1 [2.1%] case each. Nine cases [6.9%] were deferred on account of thin placenta at gestational age of below II weeks. The number of attempts has no reciprocal relationship with the frequency of complications. The study concluded that CVS is associated with least complications when the route of sampling is transabdominal and the gestational age is above II weeks. Biopsy attempts of 2-3 times is associated with a satisfactory yield of chorionic villi. The need for an improved expertise is also highlighted

Rendimiento de la translucencia nucal en 120 biopsias de vellosidades coriales / Efficiency of nuchal translucency in 120 biopsies of chorionic villies

Se estudia la correlación entre translucencia nucal (TN) y el resultado citigenético en 120 fetos en quienes se realizó biopsia de vellosidades coriales entre las 11 y 14 semanas de gestación. Se calculó el riesgo individual de aneuploidía de acuerdo a la edad materna y ajustado según edad gestacional y grosor de la TN en todos los casos. Se diagnosticaron 22 defectos cromosómicos, de los cuales 17 correspondieron a anomalías numéricas y cinco a translocaciones heredadas de uno de los padres. Descartando los casos referidos por translocaciones familiares, un riesgo superior a 1/300 logró identificar 15 de los 17 fetos con aneuploidía (detección 88 por ciento). Estos resultados, obtenidos de una población mayoritariamente de alto riesgo, confirman la validez de la TN como método de screening de defectos cromosómicos en el primer trimestre del embarazo, lo que permite extender esta metodología a la población de bajo riesgo en nuestro medio

La Biopsia de Vellosidades Corionicas como tecnica de diagnostico prenatal / The biopsy of chorionic villi as a prenatal diagnostis technique

Se realiza una revision actualizada sobre la tecnica de biopsia de vellosidades corionicas a partir de la literatura aparecida en las bases de datos MEDLINE, LILACS, y de la Literatura Cubana de Medicina desde 1989 hasta 1994. Se dan a conocer los aspectos historicos relacionados con la tecnica de biopsia de vellosidades corionicas y las tecnicas relacionadas con su aplicacion. Se concluye que a pesar de ser una tecnica invasiva, de alto costo y riesgo obstetrico, es util en el diagnostico de las malformaciones congenitas e infecciones intrauterinas que provocan danos graves al feto. Este diagnostico precoz facilita el aborto terapeutico y disminuye los riesgos obstetricos en la embarazada

Medicina fetal: diagnostico pre-natal / Fetal medicine: prenatal diagnosis

Os autores apresentam uma revisao sobre a pratica do diagnostico pre-natal na medicina fetal hoje. Os metodos mais utilizados para o diagnostico citogenetico pre-natal, como a amniocentese, a coleta de vilosidades coriais e a amostragem de sangue fetal sao descritos e analisados quanto a sua eficacia e seguranca para a gestante. Sao apresentadas tambem as novas abordagens utilizadas nesta area com objetivos diagnosticos e terapeuticos. A questao da triagem de populacoes para defeitos congenitos e discutida e problemas relativos aos custos, a utilidade e a etica no emprego desta tencologia em nosso meio sao levantados

Amostra de vilo corial: 1290 casos / Chorionic villus sampling: 1290 cases

Os autores estudaram 1.290 gestantes que se submeteram ao diagnóstico pré-natal precoce (primeiro trimestre de gestaçao) para detectar possíveis anormalidades cromossômicas no feto.O método utilizado foi a amostra de vilo corial coletada por via transcervical (AVC-TC) ou por via transabdominal (AVC-TA), dependendo das condiçoes anatômicas e da idade gestacional das pacientes. Entre as gestantes estudadas, 68,5 por cento tinham como principal indicaçao para o exame a idade avançada (igual ou superior a 35 anos); seguida de ansiedade, 11,24 por cento; filho anterior com outras anomalias cromossômicas, 10,2 por cento; filho anterior malformado, 2,9 por cento; rearranjo cromossômico nos pais, 2,6 por cento; determinaçao de sexo (nos casos de doenças ligadas ao cromossomo X), 2,5 por cento; outras indicaçoes, 2,2 por cento. Sao discutidos, neste trabalho, a importância da realizaçao da amostra de vilo corial (AVC) no primeiro trimestre da gestaçao para o diagnóstico pré-natal de alteraçoes cromossômicas no feto.

Biopsia de vilo corial por via transabdominal / Transabdominal chorionic villus sampling

Foram estudadas 66 pacientes, oriundas da Clínica privada para investigaçäo citogenética pré-natal, nas quais foram realizadas 71 biópsias de vilo corial (BVC) consecutivas, por via transabdominal, entre nove e 17 semanas de gravidez. A taxa de êxito do procedimento foi de 98,5%. Tivemos apenas um caso de abortamento espontâneo (2,9%). Como complicaçöes imediatas associadas ao procedimento, tivemos seis casos de cólica (9%), dois de sangramento vaginal (3%), quatro de perfuraçäo de membrana (6%) e três de hematoma retoplacentário (4,5%), sendo que todos evoluíram satisfatoriamente. As complicaçöes obstétricas tardias encontradas näo excederam os valores esperados na populaçäo geral. Contra-indicaçöes da via transcervical, assim como outros aspectos relacionados com a via transabdominal, foram sinalados. Concluímos ser a via transabdominal a de escolha para a realizaçäo de BVC

Efficiency of modified medium for direct chromosome preparation of the chorionic villi.

The direct chromosome preparation from the CV is a reliable method for diagnosis of the gross chromosomal anomalies and could be completed in the shortest possible time. However, direct villi preparation does not always provide sufficient or good quality metaphases. The culture medium plays an important role in achieving a good success rate. We report the efficacy of our modified medium and compared it with Chang's. The modified medium showed slightly higher successful karyotyping (68.4%) than the Chang medium (65.4%). This success rate showed no statistically significant difference. The success rate enhanced up to 92.3 per cent using our modified medium when the CV was of good quality. The higher amount of CV did not lead to a higher success rate. Any amount more than 5 mg of the CV was sufficient for direct chromosome preparation.