“…The articles selected were reviewed and the following information is summarized in Table 1: name of the first author, year of publication, country where study was done, number of participants, biological specimen, parity, statistical analysis, type of metabolomics method, a list of metabolites, direction of metabolites compared with control, and model characteristics (sensitivity, specificity and accuracy). Within this group, 16 studies investigated blood (serum/plasma) (Kenny et al 2005(Kenny et al , 2008(Kenny et al , 2010Odibo et al 2011;Bahado-Singh et al 2012, 2013, 2017a, 2017bSenyavina et al 2013;Austdal et al 2014Austdal et al , 2015aKuc et al 2014;Mukherjee et al 2014;Koster et al 2015;Chen et al 2017) and two of which also evaluated urine (Austdal et al 2014(Austdal et al , 2015a. One study used urine (Diaz et al 2013) and finally four studies used placenta (Jain et al 2004;Dunn et al 2012;Austdal et al 2015b;Zhou et al 2017), one of which assessed placental mitochondria (Zhou et al 2017).…”