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BACKGROUND: Cell-free fetal DNA (fDNA) can be detected in maternal plasma throughout human pregnancy and is rapidly cleared after delivery. fDNA measurement has clinical application in many complications of pregnancy. Our aim was to determine if fDNA could be detected in maternal plasma during pregnancy in a mouse model system. We then compared the levels of fDNA during pregnancies in which the mother and fetus were either congenic or allogenic. METHODS: C57BL/6J (H-2b) or DBA/2J (H-2d) wild-type female mice were mated to C57BL/6J mice transgenic for the enhanced green fluorescent protein (gfp) and sacrificed while pregnant. C57BL/6J female mice that had previously given birth to three to six litters after mating with transgenic males were sacrificed after delivery. We used real-time quantitative PCR amplification to detect and measure gfp sequences in maternal plasma. RESULTS: fDNA was consistently detected in maternal plasma during pregnancy and was always absent after delivery [median 211 genome equivalents (GE)/ml vs 0 GE/ml, respectively, P=0.0001]. The level of fDNA was higher in allogenic matings compared to congenic matings (median 167 GE/ml/GFP?+?fetus vs 81 GE/ml/GFP?+?fetus, respectively). CONCLUSIONS: fDNA sequences can be reliably detected in maternal plasma during murine pregnancy. Our data lends further support to the use of nonhuman species to investigate the mechanisms involved in fetomaternal trafficking. [ABSTRACT FROM AUTHOR]

BACKGROUND: Increased second-trimester levels of maternal serum HCG in IVF conceptions lead to an increased false-positive rate in Down syndrome screening. Increased levels of cell-free fetal DNA (cffDNA) in maternal plasma have been correlated with increased HCG levels. Our aim was to determine whether cffDNA levels are elevated in IVF pregnancies compared with natural pregnancies. METHODS: Sixteen archived second-trimester serum samples from IVF pregnancies were matched with five control samples from naturally conceived pregnancies per case, all carrying a singleton male fetus. cffDNA concentrations were measured by real-time PCR amplification of a Y chromosome sequence and compared with four standard second trimester serum screening markers (a-fetoprotein, estriol, HCG and inhibin A). RESULTS: Mean cffDNA levels for cases and controls were 57.9 and 57.1 genome equivalents/ml, respectively (P = 0.95). Mean observed rank (from 1 to 6) of cffDNA was 3.625 in the IVF conceived group, compared with an expected value of 3.5 (P = 0.53). No significant correlations were observed between cffDNA and serum markers. CONCLUSIONS: IVF does not affect levels of cffDNA, which appears to be independent of traditional screening markers (e.g. HCG). Therefore, cffDNA can be used as an additional serum marker (e.g. Down syndrome screening) without adjustment for IVF pregnancies. [ABSTRACT FROM AUTHOR]

Fetal cells enter the maternal circulation during most pregnancies. Their persistence for years occurs in only some women and has been associated with several autoimmune diseases such as systemic sclerosis. The objective of this study was to determine whether pregnancy history influences the persistence of fetal microchimeric cells. We reviewed all reports of studies on fetal cell microchimerism, defined as male DNA in maternal tissue, that describe individual pregnancy histories, disease diagnoses, and microchimerism status. The total numbers of pregnancies, births, and sons, the history of fetal loss (spontaneous abortion and elective termination), and the presence of a maternal autoimmune disease were tested as factors potentially associated with persistent microchimerism. One hundred twenty-four subjects from 11 studies met the inclusion criteria. Only fetal loss was significantly associated with the presence of microchimerism (odds ratio 2.4, 95% confidence interval 1.2–6.0). These results suggest that fetomaternal cell trafficking following fetal loss may be important for the engraftment of microchimeric cells in maternal tissue. This may be due to an increased amount of fetomaternal transfusion or to transfer of a cell type that is more likely to engraft. We recommend that investigators in future studies on microchimerism report detailed pregnancy information, since these data are critical for the understanding of factors that influence the development of fetal cell microchimerism. [ABSTRACT FROM AUTHOR]