New Strategy for Prenatal Diagnosis of X-Linked Disorders

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Abstract
An invasive approach is still the gold standard for prenatal diagnosis of genetic disorders. Chorionic-villus sampling, the current procedure of choice, allows an early diagnosis, but the miscarriage rate after chorionic-villus sampling is as high as 6.8 percent, and the sampling-failure rate is at least three times the rate with amniocentesis.1 Cell-free DNA circulating in maternal plasma offers the possibility of a noninvasive approach to prenatal diagnosis.2,3 This method permits determination of the sex of the fetus with 100 percent accuracy when maternal serum is analyzed during the first trimester of pregnancy.4 As a consequence, a new strategy for the prenatal diagnosis of X-linked genetic disorders is now possible. With this strategy, the sex of the fetus is determined by analysis of maternal serum between 10 and 13 weeks of gestation, followed by chorionic-villus sampling if the fetus is identified as male. If the fetus is identified as female, chorionic-villus sampling is not performed, and fetal sex is confirmed later in the pregnancy by ultrasonography.