Fetal DNA Quantitation in Peripheral Blood Is Not Useful as a Marker of Disease Severity in Women with Preeclampsia

Objective: Trophoblast migration into the maternal circulation is increased in preeclampsia and can trigger the endothelial dysfunction that characterizes the clinical disease. We hypothesised that 'fetal trafficking' is increased in women with severe preeclampsia and that the quantity of trafficking is greater in women with more severe disease. Study Design: To test the hypothesis, we used a technique that quantifies a genetic marker specific for the fetomaternal unit, that is, the SRY gene in a pregnant woman carrying a male fetus. Thirty two women with pre-eclampsia and 32 control women (women without preeclampsia) were recruited. Preeclampsia was defined according to the International Society for the Study of Hypertension in Pregnancy (ISSHP). All subjects with preeclampsia had evidence of the multisystemic nature of the disease. DNA was extracted from maternal peripheral blood and RTQ PCR analysis was performed to quantify the fetal DNA (SRY) and the total DNA (β-actin) in each sample. The ratio of fetal to total DNA was calculated and compared between women with preeclampsia and controls. Results: The women with preeclampsia and the control women did not differ in parity, blood pressure at booking, and gestational age at sampling. The groups differed significantly in age (29 ± 5.7 vs 25 ± 5.1 years; P = .007), diastolic blood pressure (DBP) at sampling (101 ± 9.5 vs 70 ± 5.5 mm Hg; P < .0001), gestational age at delivery (33 ± 4.3 vs 39 ± 1.8 weeks; P < .001), and fetal weight (1.98 ± 1 vs 3.35 ± 0.5 kgs; P < .0001). SRY was detected in 31 out of 32 women with preeclampsia and in 24 out of 32 control women (P < .001). The median SRY copy number per μL was greater in women with preeclampsia (10.6, interquartile range 12.89) than in the control women (8.6, interquartile range 20.1) but these differences were not statistically significant at P = .75. The median ratio of fetal to total DNA was almost identical in both groups (0.06, interquartile range 0.13) in PET compared to (0.06, interquartile range 0.17) the control women. No correlation was found between the quantity of fetal DNA and disease severity. Conclusion: Fetal trafficking is more likely to be detected in women with preeclampsia compared to control women but the quantity does not appear to correlate with disease severity.