"We know the perinatal period is already a time in which women are particularly vulnerable to mental health concerns," said study author Cindy Liu from Brigham and Women's Hospital in the US.
"We primarily wanted to see what factors related to the pandemic might be associated with mental health symptoms," Liu added.
For the results, the researchers launched the Perinatal Experiences and COVID-19 Effects Study (PEACE) to better understand the mental health and well-being of pregnant and postpartum individuals within the US during the Covid-19 pandemic.
Among 1,123 of these women surveyed, the study, published in the journal Psychiatry Review, found that more than 36.4 per cent reported clinically significant levels of depression.
Before the pandemic, rates of perinatal depression were generally considered to be 15-20 percent.
Furthermore, 22.7 per cent reported clinically significant levels of generalized anxiety, and 10.3 per cent reported symptoms above the clinical threshold for PTSD.
In particular, the researchers found that approximately nine per cent of the participants reported feeling a strong sense of grief, loss, or disappointment as a result of the pandemic.
This group was roughly five times more likely to experience clinically significant measures of mental health symptoms.
More respondents (18 percent) reported being "very worried" or "extremely worried" about Covid-19 related health risks.
This group was up to over four times more likely to experience clinically significant psychiatric symptoms.
The researchers were able to examine how previous mental health diagnoses, as self-reported by the respondents, impacted these rates.
They found that those with pre-existing diagnoses were 1.6-to-3.7 times more likely to have clinically significant measures of the three conditions analyzed.
But elevated psychiatric distress was observed in participants regardless of their mental health histories.
The researchers noted that the mental health experiences during the early months of the pandemic were limited due to fears surrounding Covid-19 infection risks and halting of support services.