Perinatal depression is a particolar challenge to clinicians, and its prevalence estimates are difficult to compare across studies. Furthermore,there are no studies that systematically assessed the incidence of perinatal depression. The aim of this study is to estimate prevalence, incidence, recurrence and new onset of DSM IV minor and major depression (mMD) in an unselected population of pregnant women.

1066 pregnant women were recruited at third month of pregnancy (T0), and minor/major depression (mMD) was assessed by the Structured Clinical Interview for DSM IV disorders (SCID I). The SCID I was administered at baseline evaluation (T0), the Edimburgh Postnatal Depression Scale (EPDS) was administered at third, 6th (T1), 8th (T2) month of pregnancy, and the SCID I Mood module was administered to confirme an eventual DSM-IV minor or major depression diagnosis when the EPDS score was≥13.

The pregnancy period prevalence of mMD was 12,4%.The point prevalence of mMD decreased from 8,6% at the 3rd month of pregnancy to 1,7% at the 8th month of pregnancy.The cumulative incidence of mMD was 2,2%. The weighted incidence of new onsets during pregnancy was 1,6%. The weighted percentage of recurrences during pregnancy was 3,7%.

The decline in the point prevalence during the second and third trimester of pregnancy found in our study may be attributed to psychological counselling and/or pharmacological treatment.Further studies about new onsets of depression during pregnancy are highly important in order to improve clinical prediction of risk in any individual woman.