‘Fetal side’ of the placenta: anatomical mis-annotation of carbon particle ‘transfer’ across the human placenta

ARISING FROM H. Bové et al. Nature Communications https://doi.org/10.1038/s41467-019-11654-3 (2019)

In utero exposure to environmental agents is a critical driver of diseases manifesting in childhood and adulthood1,2, and direct fetal contact with potentially harmful substances is largely determined by the ability of the material to cross the placenta, which forms a selective barrier between maternal and fetal circulations. In a recent Nature Communications article, Bové et al. present data which they report as demonstrating that ‘ambient black carbon particles reach the fetal side of human placenta’3, which centres on their demonstration that carbon particles are detectable in placental villous tissue, as visualised by two-photon microscopy. Most people will interpret the term ‘fetal side’ to mean that particles have moved from the maternal circulation into cells adjacent to the fetal circulation, yet, the data presented shows that carbon particles are contained in the placental villous tissue, and does not demonstrate transfer to the fetal side. The data presented are interesting, and the techniques used a valid way of studying entry of carbon particles into tissues, yet the conclusion as stated in the title is open to misinterpretation, which was strongly evident in media coverage of this publication...