R. J. P. Rijnders

Fetal sex determination from maternal plasma in pregnancies at risk for congenital adrenal hyperplasia

OBJECTIVE To determine first‐trimester fetal sex by isolating free fetal DNA from maternal plasma. METHODS The index case was a pregnant woman who previously delivered a girl with congenital adrenal hyperplasia. The SRY gene as a marker for the fetal Y chromosome was detected in maternal serum and plasma by quantitative polymerase chain reaction analysis. Simultaneously, we performed the same test in 25 and 19 women in the first and second trimester, respectively, and compared plasma results with fetal gender as assessed by prenatal karyotyping or as seen at ultrasound or birth. RESULTS In 44 of 45 patients at gestational ages ranging from 8 3/7 to 17 3/7 weeks, we correctly predicted fetal sex using quantitative polymerase chain reaction analysis of the SRY gene in maternal plasma. In one case, the test result was inconclusive. Overall, fetal sex was correctly predicted in 97.8% of cases (95% confidence interval 88.2%, 99.9%). CONCLUSION Amplification of free fetal DNA in maternal plasma is a valid technique for predicting fetal sex in early pregnancy. In case of pregnancies at risk for congenital adrenal hyperplasia, the technique allows restriction of dexamethasone treatment to female fetuses resulting in a substantial decrease of unnecessary treatment and invasive diagnostic tests.

Nieuwe technieken in de obstetrie: detectie van foetaal dna in maternaal bloed

SummarySince 1997 we are able to detect and quantify fetal dna in the blood of pregnant women. This pcr based technique has found a number of useful applications in current prenatal practice. In this way invasive tests with their inherent risks of iatrogenic pregnancy loss or excess blood group sensitisation can be avoided in more than half of the cases. The test also allows to restrict the administration of the scarce rhesus D immunoglobulin to those women who effectively carry an Rh D positive fetus.SamenvattingSinds 1997 zijn we in staat om uit het bloed van de zwangere dna-sequenties te herkennen en te kwantificeren die specifiek zijn voor de foetus. Deze op pcr gebaseerde techniek heeft inmiddels in de praktijk van de prenatale diagnostiek en de erytrocyten-genotypering toepassingen gevonden. Invasieve tests als vlokkentests of vruchtwaterpuncties met de risicos op iatrogeen verlies van zwangerschap of boostering van sensibilisatie kunnen zo in globaal de helft van de situaties vermeden worden. Ook laat de test toe het schaarse anti-D-immunoglobuline in de zwangerschap te reserveren voor die zwangeren die daadwerkelijk een risico op immunisatie hebben, ongeacht of ze wel of niet levende kinderen hebben.