Chorionic villus sampling

Chorionic villus sampling has gained importance as a tool for early cytogenetic diagnosis with a shift toward first trimester screening. First trimester screening using nuchal translucency and biomarkers is effective for screening. Chorionic villus sampling generally is performed at 10-12 weeks by either the transcervical or transabdominal approach. There are two methods of analysis; the direct method and the culture method. While the direct method may prevent maternal cell contamination, the culture method may be more representative of the true fetal karyotype. There is a concern for mosaicism which occurs in approximately 1% of cases, and mosaic results require genetic counseling and follow-up amniocentesis or fetal blood sampling. In terms of complications, procedure-related pregnancy loss rates may be the same as those for amniocentesis when undertaken in experienced centers. When the procedure is performed after 9 weeks gestation, the risk of limb reduction is not greater than the risk in the general population. At present, chorionic villus sampling is the gold standard method for early fetal karyotyping; however, we anticipate that improvements in noninvasive prenatal testing methods, such as cell free fetal DNA testing, will reduce the need for invasive procedures in the near future.

Prenatal diagnosis of thalassemia and hemoglobinopathies: 20 years experience at Siriraj Hospital.

Objective: To show the experience of prenatal diagnosis of Thalassemia and hemoglobinopathies in Siriraj Hospital. Methods: Hb Bart’s hydrops fetalis can be detected by DNA study from polymerase chain reaction (PCR) product in the first trimester of pregnancy either by chorionic villus sampling (CVS) or aminocentesis but in late pregnancy it can be detected unambiguous by ultrasonography at 18-20 weeks gestation, the suspected cases are confirmed by fetal blood sampling and Hb electrophoresis. Prenatal diagnosis (PND) for β-thalassemia diseases can be done at early pregnancy by direct visualization of the PCR products on electrophoresis or by dot blot analysis of amplified DNA with a set of HRP-labeled oligonucleotide probes complementary to the mutations. If the mutation is unknown. The couples have to wait for Hb analysis by HPLC or in vitro globins chain analysis from fetal blood in the second trimester. Results: The results of PND at Siriraj Hospital are summarized as Hb Bart’s Hydrops fetalis 228 cases, Homozygous Beta-Thalassemia 126 cases, and Beta Thalassemia/Hb E disease 550 cases. There are various methods of sampling namely chorionic villous sampling, amniocentesis, fetal blood sampling, ultrasound, or even combined method. There are minimal incidences of fetal loss 9 out 904 cases which comparatively give us one of the best center for prenatal diagnosis in Asia. Conclusion: Of the 904 pregnancies, the diagnosis were obtained in 891 pregnancies in which had 5 fetal loss from dead fetus in utero after fetal blood sampling in the second trimester. The other complication occurred after sampling failure.

Clinical Analysis of Prenatal Cytogenetic Diagnoses: Four-year Experience at Asan Medical Center / 대한산부인과학회잡지

OBJECTIVE: To review and evaluate a total of 2,372 cases of prenatal cytogenetic diagnoses at Asan Medical Center from 1999 to 2002. METHODS: We reviewed the medical records of the patients in whom the procedure for prenatal cytogenetic diagnosis was performed. A total of 1780 cases of amniocentesis, 455 cases of cordocentesis, and 137 cases of chorionic villus sampling were analyzed. The cytogenetic results, indications for prenatal cytogenetic diagnoses, maternal ages, and the profiles of abnormal karyotypes were reviewed. We calculated the positive predictive value of each indication for abnormal fetal karyotypes and evaluated a factor that was the most sensitive marker for abnormal fetal karyotypes. RESULTS: Among the 2,372 cases of prenatal cytogenetic diagnoses, abnormal karyotypes were identified in a total of 158 cases (6.7%). The most frequent indication for prenatal cytogenetic diagnosis was abnormal maternal serum screening (33.9%), followed by ultrasonographic abnormality (22.9%) and old age (20.0%). No significant difference was found between mean maternal age with and without abnormal fetal karyotypes after excluding balanced rearrangements and polymorphisms (31.9 +/- 5.3 vs. 32.1 +/- 4.5 years). Among the 92 cases of abnormal fetal karyotypes after excluding balanced rearrangements and polymorphisms, the most frequent indication for prenatal cytogenetic diagnosis was ultrasonographic abnormality (58.7%), followed by abnormal maternal serum screening (10.9%). The positive predictive value of ultrasonographic abnormality for abnormal fetal karyotype was 9.9%. CONCLUSION: Among the several indications for prenatal cytogenetic diagnosis, ultrasonographic abnormality could be the most predictive marker for abnormal fetal karyotypes.

Studies on the prenatal chromosomal analysis and the changes of maternal serum alpha-fetoprotein following chorionic villus sampling

Transcervical chorionic villus sampling (CVS) was performed in 174 patients between 7 & 12 menstrual weeks of pregnancy opting for prenatal diagnosis. Advanced maternal age was the most common indication for CVS (39.7%). The sampling success rate was 95.4% (166/174), representing 88.9% at 7 to 8 weeks, 98.9% at 9 to 10 weeks & 92.7% at 11 to 12 weeks gestation. In 139 of 174 patients (80%), successful sampling was accomplished in one or two catheter passages only. Four spontaneous fetal losses (2.3%) occurred. The cytogenetic analysis routinely used was the direct overnight & long-term culture methods which revealed 4 abnormalities (2.4%). To date, 90 of the women have been delivered & all infants are doing well and the remaining 65 pregnancies are continuing uneventually. Maternal serum alphafetoprotein (MSAFP) concentration was determined in 72 patients immediately before & after CVS. A significant increase of 20% or more, comparable to pre CVS levels, was noted immediately after sampling in 56 of 72 patients (77.8%). The increase in MSAFP concentration correlated with the amount of villi sampled (r = 0.498, p less than 0.001) & with the number of sampling attempts (p less than 0.05). Estimated CVS related fetomaternal hemorrhage (FMH) ranged from 0.005 to 0.1552 ml and in 5 of 72 patients (6.90%) 0.06 ml or more of FMH was noted. Two of the 5 patients had FMH of 0.1 ml or more.