We saw a 9% prevalence of antenatal depressive symptoms, which is on the lower side of the 9% to 15% prevalence of antenatal depressive symptoms reported by other studies using the EPDS.31,34
Other studies, using a variety of depression assessment tools, have reported antenatal depression prevalences of 9%–28% for predominantly middle class samples11,19,35
for low income populations. The somewhat lower prevalence in our population probably reflects both the specificity of the EPDS and the comparatively high socioeconomic position of our cohort.
Although our study is one of the first to report a higher prevalence of antenatal depressive symptoms among minority and young mothers, these associations were largely explained by differences in income, partnership status, and pregnancy intention. We saw a roughly 30% higher prevalence of antenatal depressive symptoms among women with household incomes below $40
000, although this did not reach statistical significance. However, the higher risk is consistent with several studies20,35,37
that have reported high prevalence of antenatal depression among women of lower socioeconomic position. We also found a twofold increased risk of antenatal depressive symptoms with unwanted pregnancy, which we believe has not been previously examined. By far the most powerful risk factor for depressive symptoms during pregnancy was a history of prior depression, which conferred a fourfold increased risk of antenatal depressive symptoms, similar to that reported in a small study of Norwegian mothers.1
Few studies have examined race/ethnicity as a risk factor for postpartum depression. As with antenatal depression, the higher prevalence of postpartum depressive symptoms that we saw among minority mothers was explained by financial hardship. Although some studies report no associations of postpartum depression with socioeconomic position,11,39
others have found that financial difficulties,19,29
or low education36
are more prevalent among women with postpartum depression. We saw a nearly threefold increased risk of postpartum depression among mothers who had low birthweight infants. One study reported increased risk of postpartum depression with poor infant health,36
but another found reduced risk of depression among women who had delivered before term.29
The single strongest risk factor for postpartum depressive symptoms was depressive symptoms during pregnancy, as has been seen consistently.34,40
What is known on this topic
Although major depression is associated with low socioeconomic position, available data are contradictory regarding the association of sociodemographic factors with antenatal and postpartum depression.
What this paper adds
Our report confirms that women living in disadvantage are at higher risk of depressive symptoms during the childbearing year. Maternal minority status does not confer risk independent of its socioeconomic correlates, a question that had never been satisfactorily addressed.
To the extent that depressive symptoms before, during, and after pregnancy represent a consistent underlying depressive syndrome, it is possible that depressive symptoms preceding pregnancy might increase social and economic risk (such as unemployment or lack of a partner); if this were the case, these social and economic risks might seem as spurious “predictors” of antenatal and postpartum depression. To our knowledge, no study has examined whether these risk factors predict depressive symptoms among women with no history of depressive symptoms. Lack of a partner and unwanted pregnancy remained associated with antenatal depressive symptoms among women with no history of depressive symptoms, suggesting that the risks associated with partnership status and pregnancy intention are not spurious artefacts of an antecedent depressive symptoms. For postpartum depressive symptoms, financial hardship was a risk factor whether or not women had experienced prior depressive symptoms, suggesting that poverty precedes postpartum depression, rather than the alternative that depression leads to poverty.
This study had several limitations. Chief among these is our reliance on a self reported screen of depressive symptoms, rather than clinician diagnosis. Although the EPDS has been validated in a broad range of populations,41
it remains possible that cultural and/or economic factors may have caused women to over‐report or under‐report depressive symptoms. Social desirability bias may particularly affect minority42
and lower socioeconomic participants,43
leading them to under‐report symptoms of depression,42
and us to underestimate associations between these factors and depressive symptoms. The timing of exposures and the onset of depressive symptoms is not established for every exposure; in particular, the examination of social support and depression is effectively cross sectional and should be interpreted with caution (as in most other studies). While 23% of the cohort who responded to the mid‐pregnancy questionnaire did not return the postpartum questionnaire, the proportion responding was similar among those with (75%) and without (77%) depression mid‐pregnancy. This suggests that non‐response neither substantially reduced our estimate of the prevalence of depression, nor created bias in ascertaining predictors of depression. If anything, the higher loss to follow up among minority and disadvantaged mothers might have caused us to slightly underestimate associations between lower socioeconomic status and depressive symptoms.
Because of their increased risk of antenatal and postpartum depression, women facing socioeconomic hardship and those with poor pregnancy outcomes should be targeted for depression screening, prevention, and treatment.
In summary, we found that maternal race/ethnicity is not an independent predictor of antenatal or postpartum depressive symptoms. Instead, the apparently higher risk among minority women seems to result from financial hardship and, for postpartum depressive symptoms, poor pregnancy outcome. The higher risk of antenatal and postpartum depressive symptoms associated with young maternal age is largely explained by financial hardship, unwanted pregnancy, and lack of a partner. The fact that financial hardship and partnership status predicted depressive symptoms among women with no history of depressive symptoms suggests that these factors are likely to predate, and perhaps cause, depression during pregnancy and the postpartum.