Low serum placental lactogen at term is associated with postnatal symptoms of depression and anxiety in women delivering female infants

The placenta is arguably the most important organ of the body, but paradoxically the most poorly understood. During its transient existence, it performs actions that are later taken on by diverse separate organs, including the lungs, liver, gut, kidneys and endocrine glands. Its principal function is to supply the fetus, and in particular, the fetal brain, with oxygen and nutrients. The placenta is structurally adapted to achieve this, possessing a large surface area for exchange and a thin interhaemal membrane separating the maternal and fetal circulations. In addition, it adopts other strategies that are key to facilitating transfer, including remodelling of the maternal uterine arteries that supply the placenta to ensure optimal perfusion. Furthermore, placental hormones have profound effects on maternal metabolism, initially building up her energy reserves and then releasing these to support fetal growth in later pregnancy and lactation post-natally. Bipedalism has posed unique haemodynamic challenges to the placental circulation, as pressure applied to the vena cava by the pregnant uterus may compromise venous return to the heart. These challenges, along with the immune interactions involved in maternal arterial remodelling, may explain complications of pregnancy that are almost unique to the human, including pre-eclampsia. Such complications may represent a trade-off against the provision for a large fetal brain.

i) To highlight the increasing use in the literature of unvalidated cut-off scores on the Edinburgh Depression Scale (EDS/EPDS), as well as different wording and formatting in the scale; ii) to investigate and discuss the possible impact of using an unvalidated cut-off score; iii) to highlight possible reasons for these 'errors'; and iv) to make recommendations to clinicians and researchers who use the EDS/EPDS. A convenience sample of studies that have used unvalidated cut-off scores, or different formatting, are cited as evidence that these types of 'errors' are occurring fairly frequently. Examination of previous data from one of the authors is undertaken to determine the effect of using an unvalidated cut-off score. Many studies report rates of high scorers on the EDS/EPDS using different cut-off scores to the validated ones. The effect of doing this on the overall rate can be substantial. The effect of using different formatting is not known, though excluding items from the EDS/EPDS must also make a substantial difference. We recommend that i) the validated score of 13 or more is used when reporting on probable major depression in postnatal English-speaking women, and 15 or more when reporting on antenatal English-speaking women; ii) that the wording used is "13 or more" (or equivalent), and not other terms that may cause confusion (e.g., '>12'; 'more than 12'; '13' etc), iii) if a different cut-off score to the validated one is used, a clear explanation is given as to why this has been done; and iv) that the scale should be worded and formatted as originally described by its authors.