Unique biochemical and physical challenges to both mother and fetus are observed during human pregnancy, and the placenta plays an important role in protecting the fetus and supporting its development. Consequently, many pregnancy complications are associated with altered placental biochemistry and structure. Here we have further developed a combination of analytical tools for determining the tissue metabolome of placental tissue by applying a methanol/water/chloroform extraction method followed by analysis of the polar fraction (methanol/water) using GC–ToF–MS and of the non-polar fraction (chloroform) using UPLC–LTQ–Orbitrap–MS. This combination maximises the number of different metabolites detected and is the first holistic investigation of placental tissue applying UPLC–MS. Placental tissue differs between early and late first trimester pregnancies in that the developing placenta is exposed to significantly different oxygen tensions and undergoes a change from histiotrophic to haemotrophic nutrition. Application of these metabolomic methods detected 156 unique and chemically identified metabolites that showed statistically significant differences (P