Volume 163 Number 3 bara J. Burkett, PhD, provided invaluable statistical as- sistance. The technical assistance of Iris Coiner, Jean DePiro, Rachel Baughman, Patti Roach, Bonnie Law- son, and Carolyn Morris was much appreciated. REFERENCES 1. Hogge WA, Schonberg SA, Golbus MS. Chorionic villus sampling: experience of the first 1000 cases. AM] OBSTET GYNECOL 1986; 154: 1249-52. 2. Wade RV, Young SR. Analysis of fetal loss after transcer- vical chorionic villus sampling - a review of 719 patients. AM] OBSTET GYNECOL 1989;161:513-9. 3. Clark BA, Bissonnette ]M, Olson SB, Magenis RE. Preg- nancy loss in a small chorionic villus sampling series. AM ] OBSTET GYNECOL 1989;161:301-2. 4. Rhoades GG, Jackson LG, Schlesselman SE, et al. The safety and efficacy of chorionic villus sampling for early prenatal diagnosis of cytogenetic abnormalities. N Engl] Med 1989;320:609-17. 5. Canadian collaborative CVS-amniocentesis clinical trial group. Multicenter randomized clinical trial of chorion villus sampling and amniocentesis. Lancet 1989; 1: 1-6. Chorionic villus sampling vs amniocentesis 6. Seeds ]W, Cefalo RC. Sonographic gestational age assign- ment. In: Practical obstetrical ultrasound. Rockville, Maryland: Aspen Publishers, Inc., 1986:49-68. 7. Hogge WA, Schonberg SA, Golbus MS. Prenatal diagnosis by CVS: lessons of the first 600 cases. Pre nat Diagn 1985;5:393-400. 8. Gibas LM, Grujic S, Barr MA,]ackson LG. A simple tech- nique for obtaining high quality chromosome prepara- tions from chorionic villus sampling using FdU synchro- nization. Prenat Diagn 1987;7:323-7. 9. Evans MI, Drugan A, Koppitch FC, Zador IE, Sacks A], Sokol R]. Genetic diagnosis in the first trimester: the norm for the 90s. AM] OBSTET GYNECOL 1989; 160: 1332-9. 10. Brambati B, Oldrini A, Ferrazzi E, Lanzani A. Chorionic villus sampling: an analysis of the obstetric experience of 1000 cases. Prenat Diagn 1987;7:157-69. 11. Wright D], Brindley BA, Koppitch FC III, Drugan A, Johnson MP, Evans MI. Interpretation of chorionic villus sampling laboratory results is just as reliable as amnio- centesis. Obstet Gynecol 1989;74:739-44. 12. Browner WS, Black D, Newman TB, Hulley SB. Esti- mating sample size and power. In: Hulley SB, Cummings SR, eds. Designing clinical research. Baltimore: Williams & Wilkins, 1988: 139-50. Second-trimester placental biopsy for rapid fetal karyotyping A. D. Cameron, MB, ChB,' A. M. Mathers, MB, ChB,' S. Wisdom, MB, ChB,' J. Johnstone, RGN,' J. R. M. MacKenzie, MB, ChB,' J. J. Walker, MB, ChB,' S. J. Imrie, BSe,' G. W. Lowther, BSe, DipRCPath,b andJ. M. Connor, BSe, MD b Glasgow, Scotland Since January 1988 the technique of first-trimester chorionic villus sampling (placental biopsy) has been extended to include cases in the second trimester. To date, 40 procedures have been performed. The main indication for the late chorionic villus sampling was a low serum u-fetoprotein value in association with an increased risk for Down syndrome (n = 28), abnormal ultrasonographic finding (n = 7), and failed amniotic cell culture (n = 3). Successful karyotype results were achieved in all but two cases. Most results were obtained within 48 hours with direct cytogenetic techniques. No cases of mosaicism were found. The highest yield of abnormal karyotypes was obtained from the cases with abnormal ultrasonographic findings (one trisomy 21, two 45,X). One case of trisomy 21 was identified in the 28 cases of low serum u-fetoprotein. No spontaneous losses have occurred. The technique is easy to learn, does not differ from first-trimester procedures, and may have a lower complication rate than cordocentesis.The reporting of cases to the CVS Newsletter should help evaluate late chorionic villus sampling as another method for rapid fetal karyotyping. (AM J OBSTET GVNECOL 1990;163:931-4.) Key words: Placental biopsy, rapid fetal karyotyping, chorionic villi Amniocentesis performed in the second trimester of pregnancy is still the "gold standard" test for the de- tection of fetal karyotype abnormalities. The disadvan- From the Department of Obstetrics and Gynaecology, Glasgow Royal Maternity Hospital," and the Department of Genetics, Duncan Guthrie Institute of Medical Genetics. b tage of this technique is that results are not available for 2 or 3 weeks. This is particularly unacceptable in late pregnancy, when knowledge of the fetal karyotype is essential for obstetric management when certain structural defects are present in the fetus. Presented at the Tenth Annual Meeting of the Society of Perinatal Obstetricians, Houston, Texas, january 23-27,1990. Reprint requests: A. D. Cameron, MB, CkB, Glasgow Royal Mater- nity Hospital, Rottenrow, Glasgow, G4 ONA, United Kingdom. 6/6/22352 Chorionic villus sampling or placental biopsy, unlike amniocentesis, does not require culture for immediate karyotype analysis. The direct method as described by Simoni et al. I yields results within 48 hours. The tech- nique has been shown to be feasible when performed 931