Supplementary Material for: Cell-Free Placental DNA in Maternal Plasma in Relation to Placental Health and Function

<i>Background:</i> While cell-free placental DNA (cfp-DNA) increases in response to certain pathological conditions, confounding variables, such as placental size, may also contribute to its release. Furthermore, the relationship between cfp-DNA and maternal serum proteins has not been well investigated. <i>Objective:</i> To analyze plasma cfp-DNA levels and correlate with measurable placental parameters, maternal serum proteins, or pathologic conditions reflecting placental dysfunction. <i>Method:</i>Methylated fraction of <i>RASSF1A</i> was quantified in maternal plasma as a measure of cfp-DNA in a cohort of 86 pregnant women. <i>Results:</i> Placental dimensions or weight had no impact on cfp-DNA levels in noncomplicated pregnancies (n = 63). However, an association between β-hCG and cfp-DNA levels (p = 0.0012) was detected. Complications occurred in 23 pregnancies including chromosomal abnormalities, gestational hypertension, intrauterine growth restriction, and preterm birth. There was overall a skewed distribution (1 SD from mean) for cfp-DNA in the abnormal group, although due to the small number of samples for each pathology, we provide only descriptive data to assess possible trends in cfp-DNA variation.<i>Conclusion:</i> While cfp-DNA levels outside of the normal range may reflect placental distress, this relationship may be masked by a number of physiological confounders. The independence of cfp-DNA from β-hCG levels commonly assessed in pregnancy need to be further addressed.