Final answer:
The percentage of women with a history of depression before pregnancy and a more chronic pattern among those diagnosed with postpartum depression is not explicitly mentioned. However, the onset of depression before pregnancy can increase the risk of postpartum depression.
Step-by-step explanation:
The percentage of women whose depressive episodes began before pregnancy with a more chronic pattern among the 21% of mothers diagnosed with postpartum depression (PPD) is not explicitly mentioned in the provided references. However, it is important to note that postpartum depression can occur both in women with a history of depression before pregnancy and in women who experience depressive episodes for the first time after giving birth.
In general, the onset of depression before pregnancy, especially if it has a chronic pattern, can increase the risk of developing postpartum depression. Factors such as hormonal changes during pregnancy and the postpartum period, sleep deprivation, and the challenges of adjusting to parenthood can contribute to the development of postpartum depression.
Overall, further research and studies are needed to determine the specific percentage of women with a history of depression before pregnancy and a more chronic pattern among those diagnosed with postpartum depression.