Volume 178, Number 5AmJ Obstet Gynecol

tween fetal Sp02 and scalp blood pH in fetuses with un­eventful neonatal outcome-as did Szabo et al.-is thusnot sufficient. Large randomized controlled trials arenecessary to validate pulse oximetry as a tool for fetalmonitoring in clinical practice.

Bruno Carbonne, MD, Francois Goffinet, MD, BrunoLanger; MD, and theFrench Study Group on Fetal Pulse

OximetryDepartment of Obstetrics and Gynecology, Hbpital Saint-Antoine,F 75012 Paris, France

REFERENCES

1. Carbonne B, Cudeville C, Sivan H, Cabrol D, Papiernik E. Fetaloxygen saturation measured by pulse oximetry during labourwith clear or meconium-stained amniotic fluid. Eur] ObstetGynecol Reprod Bioi 1997;72 Suppl1:S51-5.

2. Carbonne B, Maillard F, Langer B, Goffinet F, Cudeville C,Tardif D, et al. Meconium aspiration in fetuses monitored withcardiotocography, scalp blood analysis and pulse oximetry dur­ing labor: what is relevant? [abstract]. In: Proceedings of theThird World Congress of Perinatal Medicine; 1996 Oct 20-24;San Francisco, California. San Francisco: The Congress; 1996. p.44.

3. Johnson N,Johnson VA,Bannister,], McNamara H. The effectof meconium on neonatal and fetal reflectance pulse oximetry.JPerinat Med 1990;18:351-5.

6/8/89471

Rapidprenatal detection of aneuploidies by fluores­cent polymerase chain reactionTo the Editors: Pert! et al. (Pertl B, Kopp S, Kroisel PM,Hausler M, Sherlock], Winter R, et al. Quantitative fluo­

rescence polymerase chain reaction for the rapid prena­

tal detection of common aneuploidies and fetal sex. Am]Obstet Gynecol 1997;177:899-906) have recently re­

ported a multiplex fluorescent polymerase chain reac­

tion (PCR) technique for the rapid prenatal detection of

common aneuploidies.We have read this article very carefully because the au­

thors' previous report contained a very serious error in achromosome 21 marker (D21S1414). Although our criti­cism article! concerning that mistake will be availablesoon, we must also bring this to the attention of the read­ers of this journal because Pertl et al. have repeated theirserious mistake in this study. Not only have they repeatedthe mistake by using the wrong marker, they also have

presented inconsistent data, which casts doubt on their

results and on the fluorescent PCR technique.

Because we work in a similar field,2 we screened sev­

eral STR markers on chromosome 21 to amplify fetal de­

oxyribonucleic acid isolated from amniotic fluid to de­tect chromosomal aneuploidies in multiplex fluorescent

PCR. Our results, with use of additional markers, will be

presented soon. It was during this screening that the ho­mology between the two D21 markers used by Pertl et al.

was found.Pertl et al. used four chromosome 21 markers, two of

Letters 1101

which are D2lSll and D21S1414. Previous studies--f have

shown that they are complementary and are actually the

same sequence. Rather than two primer pairs amplifyingtwo independent STR markers and thus providing con­

firmation of each other, the two primer sets used by Pertlet al. (D2ISll and D21S1414) amplify the same repeat se­

quence and must provide the same profile. The only dif­

ference in these two primer sets is a slightly different po­

sition in the sequence, which is not linked to the

repeating section.

However, the main problem with the report ofPertl et

al. is that they published different data regarding these

two markers. Because D2IS11 and D2lS1414 markers

must give the same results, the number of heterozygous

and homozygous patients must also be the same for thesetwo markers. However, these authors reported different

numbers in normal blood samples, normal amniotic

fluid, and even in trisomy 21 samples.Because the evidencel- 3 shows that D2lS11 and

D21S1414 are the same and therefore must provide the

same results, the reported data are only acceptable if the

authors can present different results for the two markers

from the same sample. In our experience the fluorescent

PCR technique is very reliable and could not cause those

mistakes. Therefore a different explanation is required

from the authors.Tamas tsa; MD, and ZoUcin Papp, DSc

Department of Obstetrics and Gynecology, Semmelweis UniversityMedical School, Baross u. 27, Budapest, H-1088, Hungary

Ian Findlay, PhDMolecular Oncology, Institute of Pathology, Algernon Firth Building,University of Leeds, Leeds, United Kingdom LS2 9LN

REFERENCES

1. T6th T, Findlay I, Nagy B, Quirke P, Papp Z. Prenatal detectionof trisomy 21 by fluorescent polymerase chain reaction: impor­tance of primer selection and criticism of an earlier report.Hum Genet 1997;101:383.

2. T6th T, Findlay I, Papp C, Toth-Pal E, Marton T, Nagy B, et al.Prenatal detection of trisomy 21 and 18 from amniotic fluid byquantitative fluorescent polymerase chain reaction. ] MedGenet 1998;35:126-9.

3. Utah Marker Development Group. A collection of orderedtetranucleotide-repeat markers from the human genome. Am]Hum Genet 1995;57:619-28.

6/8/89478

ReplyTo theEditors: We are and have been aware for years that

the D21S11 and D21S1414 primers amplify the same re­

gion of chromosome 21. However, far from being a "seri­ous mistake," we have decided to include both primers in

the multiplex assays to provide further evidence of any

detectable aneuploidy. Some of the observed discrepan­

cies suggest a possible polymorphism in the adjacent de­oxyribonucleic acid regions and do not invalidate our re­sults. Findlay et al. continue to miss the fact that we use