Effectiveness of the model for prenatal control of severe thalassemia.

OBJECTIVE: The aim of the research was to determine effectiveness of the model for prenatal control in reducing new cases of severe thalassemia. METHODS: Pregnant women at six tertiary centers were recruited to follow the model, consisting of (1) carrier screening using mean corpuscular volume (for alpha-thal-1 and beta-thal) and CMU-E screen (for HbE trait), (2) carrier diagnosis, (3) the couples at risk were counseled and offered prenatal diagnosis, and (4) termination of affected pregnancy. All neonates were evaluated for thalassemia. RESULTS: Of the 12,874 recruited pregnancies, 7008 were valid for analysis. Of them, 281 couples were identified to be at risk, Of the 281, 58 affected fetuses were identified and 55 pregnancies were terminated, whereas three did not accept pregnancy termination. All 6727 neonates at no risk were proven to be unaffected. The model had sensitivity and positive predictive value of 100% and 20%, respectively. The model could detect all of affected fetuses. CONCLUSION: The model could prenatally identify affected fetuses with a detection rate and negative predictive value of 100%. The model was highly effective to prenatally detect affected fetuses with an acceptable false positive rate.

Chorionic villus sampling for early prenatal diagnosis at Bhumibol Adulyadej Hospital.

OBJECTIVE: To evaluate results of chorionic villus sampling for early prenatal diagnosis at Bhumibol Adulyadej Hospital. DESIGN: Retrospective descriptive study. SETTING: Perinatal unit, Department of Obstetrics and Gynaecology, Bhumibol Adulyadej Hospital. SUBJECTS: Three hundred and eighty three women were enrolled to chorionic villus sampling at the perinatal unit, Department of Obstetrics and Gynecology, Bhumibol Adulyadej Hospital, from November 10,1997 to October 17, 2006. RESULTS: During the present study periods three hundred and eighty three women were recruited, of these chorionic villus sampling for chromosome diagnosis were performed on 355 while 6 were for abnormal Thalassemia screening. Twenty two cases were excluded because ultrasound examination showed anembryonic pregnancy or fetal demise in utero in 13 cases, multiple fibroids in 4 cases, large area of placental hemorrhage in 3 cases, 1 case of multiple pregnancy and in 1 case the placenta was in an inappropriate position. The most common indication was elderly gravidarum (95.84%). Other indications were abnormal Thalassemia screening, abnormal ultrasound findings, family chromosome disorder previous Down syndrome, and severe oligohydramnios. The authors found eleven cases of chromosome abnormalities, four cases of maternal cell contamination and three cases of failed tissue culture (two cases from transcervical chorionic villus sampling and one case from transabdominal chorionic villus sampling) and two cases of mosaicism. There were two fetal losses in the present study and all the babies from the normal chromosome result looked normal. Second trimester amniocentesis following chorionic villus sampling was required due to maternal cell contamination, mosaicism and failed tissue culture. (2.77%) All cases had follow-up ultrasound scan during 18-20 weeks. CONCLUSION: The authors found that chorionic villus sampling is a possible alternative technique for prenatal diagnosis of cytogenetic abnormalities and abnormal Thalassemia screening in Thailand. It probably has a slightly higher rate of failed tissue culture and maternal cell contamination than amniocentesis, but it is generally done earlier in pregnancy than amniocentesis and is particularly advantageous for detecting certain genetic conditions.