Depression is thought to affect at least one in five women globally in the later stages of pregnancy and shortly after birth, and is characterised by low mood and feelings of hopelessness, and is also brought on by a number of other factors that can include life events such as bereavement, and changes in brain chemistry.
Previous work from the researchers suggested that depression during pregnancy may affect the development of the baby while in the womb, as well as affecting bonding between mother and child after birth.
Now, the same team has shown that depression or anxiety can reduce the enzyme in the placenta that breaks down the "stress hormone" cortisol, possibly causing more foetal exposure to the hormone.
The foetus may also undergo epigenetic changes under stress, where underlying DNA stays the same but expression of that DNA is altered, perhaps affecting mental health during childhood.
The team argued the problem is more common in low and middle-income countries, and hence more resources are needed in these areas to help expectant and new mothers.
"In severely deprived regions where there are wars, political violence, food insecurity, and little help after natural disasters, healthcare workers have little time or resources to meet basic physical needs, let alone mental health ones like maternal depression," said Vivette Glover, researcher at the Imperial College London.
The report highlights the specific mental health requirements of mothers and children in poorer countries that are not necessarily relevant to high-income countries.
"Women are more likely than in richer countries to experience intimate partner violence and have little social support. Furthermore, unintended pregnancies are more common, as are malnourishment, infections, and crowded living conditions," Glover added.
Maternal depression in these countries is also more likely to result in poor nutrition, increased substance use, inadequate antenatal care, pre-eclampsia, low birthweight, preterm delivery, and suicide.
The research, published in the journal The Lancet Psychiatry focused mainly on low and middle-income countries.
