摘要：Object.ve: Measurement.of cell- free fet.l (cff) DNA in mat.rnal plasma may have clinical applicat.on in prenat.l screening for fet.l Down syndrome and preeclampsia. Lit.le is known regarding t.e t.ssue of origin of t.ese fet.l-derived sequences. We t.st.d t.e hypot.esis t.at.if t.e placent. is t.e major cont.ibut.r of cff DNA, t.en an increased placent.l volume should be associat.d wit. higher mat.rnal plasma cff DNA levels. St.dy design: We enrolled 143 pregnant.women who underwent.first.t.imest.r placent.l volume measurement.using 3- dimensional ult.asonography. Cff DNA in mat.rnal plasma on t.e day of t.e scan was quant.fied by real-t.me polymerase chain react.on (PCR) amplificat.on of a Y- chromosome sequence. t.e associat.on bet.een measured placent.l volume and mat.rnal plasma cff DNA levels was analyzed along wit. relevant.clinical variables. Result.: t.e median (25t., 75t. percent.les) mat.rnal plasma cff DNA level was 16.9 genome equivalent. (GE)/mL (10.8, 28.7). Raw values were adjust.d for gest.t.onal age and mat.rnal body mass index. Result.: t.e median (25t., 75t. percent.les) placent.l volume was 53.2 mL (43.0, 64.7), and median placent.l quot.ent.(rat.o of placent.l volume t. fet.l crown-rump lengt.) was 1 mm2 (0.8, 1.1). Based on mult.variat. linear regression analyses, neit.er of t.e above placent.l measurement. showed a significant.associat.on wit. mat.rnal plasma cff DNA levels (P = .43 and .43, respect.vely). A modest.associat.on was found bet.een plasma cff DNA levels and gravidit. (P = .03). Conclusion: Our dat. did not.show a significant.associat.on bet.een eit.er t.e placent.l volume or placent.l quot.ent. and mat.rnal plasma cff DNA levels. We speculat. t.at.it.is t.e ext.nt.of placent.l apopt.sis t.at.primarily affect. t.e amount.of cff DNA released int. t.e mat.rnal circulat.on.