Testing normality of fetal DNA concentration in maternal plasma at 10-12 completed weeks' gestation: a preliminary approach to a new marker for genetic screening.
OBJECTIVE
To test the distribution of fetal DNA in maternal plasma expressed as gen/eq in a population of normal pregnancies.


METHODS
Peripheral blood samples were obtained from 63 women (85% > or =35 years of age at delivery) bearing a euploid male fetus. Each patient underwent chorionic villus sampling (CVS) for karyotype analysis and/or beta thalassemia screening. Ultrasound scanning was used to determine gestational age. At 10-12 weeks' gestation, a peripheral blood sample was collected followed by CVS. To detect the Y chromosome specific sequences (SRY) quantitative polymerase chain reaction (PCR) analysis was used. Normal distribution of the data was tested by means of the Kolmogorov-Smirnov (KS) test. A Symmetry test (reliability p>0.05) was used to evaluate the reliability of the median.


RESULTS
Only after natural logarithmic transformation did the data display a normal distribution. The median value of fetal DNA was 23.3 gen/eq (range 2.08-195), interquartile range 18.57-45.4. A Pearson test showed a significant correlation between gestational age and fetal DNA concentration (r=0.25, p=0.045).


CONCLUSIONS
The present finding is a preliminary step towards a possible integration of fetal DNA with other variables (biochemical and/or ultrasound). It may serve to improve the discrimination of the screening for genetic diseases in the first trimester. Because of the relatively high dispersion, adjustments for possible covariates would appear to be necessary in further studies.
Farina
Antonio
A
Institute of Histology and General Embryology, University of Bologna, Italy. farina@alma.unibo.it
Caramelli
Elisabetta
E
Concu
Manuela
M
Sekizawa
Akihiko
A
Ruggeri
Roberto
R
Bovicelli
Luciano
L
Rizzo
Nicola
N
Carinci
Paolo
P
D015193:Chorionic Villi Sampling; D002869:Chromosome Aberrations; D004247:DNA / Q000097:blood*; D004314:Down Syndrome / Q000175:diagnosis; D005260:Female; D005333:Fetus; D005865:Gestational Age; D006801:Humans; D007621:Karyotyping; D008297:Male; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011296:Prenatal Diagnosis; D016216:Ultrasonography, Prenatal; D017086:beta-Thalassemia / Q000235:genetics
D004247:DNA