First-trimester fetal sex prediction by deoxyribonucleic acid analysis of maternal peripheral blood

OBJECTIVES: We investigated whether the number of weeks of gestation influe nces the accuracy of first-trimester fetal sex prediction by analysis of de oxyribonucleic acid extracted from whole maternal blood. A comparison was a lso made to determine whether a difference exists between this approach and the deoxyribonucleic acid analysis of transcervical cells performed on the same group of subjects. STUDY DESIGN: Deoxyribonucleic acid was isolated from 50 maternal blood sam ples taken between gestational weeks 7 and 11. The sex of the fetus was ass essed by nested polymerase chain reaction specific for the amelogenin gene. A receiver-operating characteristic curve analysis was used to correlate t he accuracy of fetal gender prediction with the gestational age and also to compare the goodness of the 2 methods under investigation. RESULTS: Analysis of the receiver-operating characteristic curve provided a cutoff value of 9 weeks 4 days of gestation for both tests, indicating tha t a higher degree of accuracy in the sex assignment was obtained in those s amples taken before or at this time. However, this difference was statistic ally significant only for analysis of deoxyribonucleic acid from maternal b lood. The comparison between tests of deoxyribonucleic acid from maternal b lood and from transcervical cells showed that the first approach is better, although a statistically significant difference was not found. CONCLUSION: Analysis of maternal blood deoxyribonucleic acid is a better ap proach than analysis of transcervical cell deoxyribonucleic acid in fetal s ex prediction. The highest degree of accuracy is obtained when blood is dra wn before 10 weeks of gestation. This can be important when sampling of cho rionic villi should be avoided because of the risk of an X-linked disease w hen the fetal sex is female.