Fig. 4.

Paternally expressed gene 3 (PEG3), human placental lactogen (hPL) signalling and maternal psychological adaptation to pregnancy. Model 1: prenatal depression causes reduced PEG3 and reduced hPL expression. Model 2: reduced PEG3 initiates prenatal depression through regulation of placental lactogen production. Model 3: an adverse intra-uterine environment causes reduced PEG3 expression limiting placental signalling and establishing a cycle of aberrant placental gene expression, aberrant signalling and abnormal maternal mood.