Background: Antenatal anxiety has received increased attention with regards to both its impact on infant outcomes and as a risk factor for postnatal depression. The measurement of anxiety in the perinatal setting, however, has proven to be challenging. The aims of the present study are to: determine whether antenatal anxiety as measured by the Brief Measure of Worry Severity (BMWS) is a significant predictor of postnatal depression (PND); examine the psychometric properties of a new measure of anxiety - the BMWS - in an antenatal sample; and examine the comparative capacity of the BMWS to the Speilberger State Trait Anxiety Inventory (STAI) in predicting PND.
Method: A sample of 748 women completed the BMWS and STAI during the third trimester of pregnancy and returned the Edinburgh Postnatal Depression Scale (EPDS) at 8 weeks postpartum.
Results: Women with high antenatal anxiety on the BMWS were 2.6 times more likely to have probable PND than those with low scores, even after controlling for confounding factors, including level of antenatal depression on the EPDS. In contrast, the STAI was no longer a significant predictor of PND after controlling for these variables. The BMWS has good construct validity, with scores on this scale correlating strongly with scores on other measures of anxiety, depression and perinatal risk.
Limitations: When compared to those who participated in the follow-up at 8 weeks postnatally, those who did not participate appeared to be at greater risk of developing PND, raising the possibility of attrition bias within this sample.
Conclusions: The findings from this study suggest that the BMWS has utility in measuring antenatal anxiety in both clinical and research settings and that antenatal anxiety is an important precursor of PND.