Cancer during pregnancy has been associated with (pathologically) small for gestational age offspring, especially after exposure to chemotherapy in utero. These infants are most likely growth restricted, but sonographic results are often lacking. In view of the paucity of data on underlying pathophysiological mechanisms, the objective was to summarize all studies investigating placental pathology related to cancer(treatment). A systematic search in PubMed/Medline, Embase (OVID) and SCOPUS was conducted to retrieve all studies about placental pathology in cancer during pregnancy or after cancer treatment, published until August 2020. The literature search yielded 5784 unique publications, of which 111 were eligible for inclusion. Among them, three groups of placental pathology were distinguished. First, various histopathologic changes including maternal vascular malperfusion have been reported in pregnancies complicated by cancer and after cancer treatment exposure, which were not specific to type of cancer(treatment). Second, cancer(treatment) has been associated with placental cellular pathology including increased oxidative damage and apoptosis, impaired angiogenesis and genotoxicity. Finally, involvement of the placenta by cancer cells has been described, involving both the intervillous space and rarely villous invasion, with such fetuses are at risk of having metastases. In conclusion, growth restriction is often observed in pregnancies complicated by cancer and its cause can be multifactorial. Placental histopathologic changes, cellular pathology and genotoxicity caused by the cancer(treatment) may each play a role.