Association between depressive symptoms during pregnancy and risk of pre-term delivery.

Sir, We read with great interest a recent paper by Li et al. (2009) on the association between the presence of depressive symptoms during pregnancy and the risk of preterm delivery. The authors evidenced a significant association, in accordance with the results of several other previous studies. They cite in their article a study we published in 2002 on the role of anxiety and depression in the onset of spontaneous preterm labor (Dayan et al., 2002). To quote a part of the discussion Li et al. developed in their article, our study uses ‘a slightly different outcome’ than preterm delivery, a point we totally agree with. As we already stressed in our article, preterm labor and preterm delivery are two complications that should be clearly distinguished from one another. It is however, quite surprising that Li et al. completely omitted to cite a article we published in 2006 that reports, on the same cohort of nearly 700 women, the analysis of the effects of antenatal depression and anxiety on spontaneous preterm birth (Dayan et al., 2006). Based on the methodological discussion we already had in our article, we would like to comment on a few points relating to Li et al.’s article. The first point concerns the self-questionnaire used to assess depression Center for Epidemiologic Studies Depression Scale (CES-D), which has never been validated during pregnancy. The CES-D includes several items describing somatic symptoms commonly experienced by the women during the first trimester of pregnancy that may be misleading as indicators of depression in pregnancy. The authors stated that the removal of such items did not change the hazard ratios relating preterm delivery to depressive symptoms but, to our knowledge, there are no validation studies of the CES-D without those items. The choice of another tool, validated during pregnancy—for instance the Edinburgh Postnatal Depression Scale (Murray and Cox, 1990)—would have been more appropriate. Our second comment relates to the outcome variable. We think that it would have been of interest to differentiate between spontaneous and indicated preterm deliveries. These two outcomes broadly differ in their etiology and perhaps also in their association with depression. Our third and final comment refers to the issue of multiple pregnancies; it is a known and strong obstetric risk factor of preterm delivery, which could act as a confounding factor. The strength of the association between depression and preterm delivery may also be supposed to be different than with a singleton. Since the expected number of multiple pregnancies would probably not be sufficient to make that variable part of the potential confounders or effect modifiers considered in the analysis, we think that it would have been advisable to exclude those cases, as we did in our own studies. Li et al.’s article provides an additional argument in favor of an association between prenatal depression and preterm birth. Discrepancies in the results of recent prospective studies nevertheless exist. We think that a large longitudinal study based on psychological instruments validated during pregnancy, with repeated assessments of depressive symptoms throughout the pregnancy, and also focusing, as proposed by Li et al., on potential interactions with socio-demographic characteristics, reproductive history or presence of other stressors, could help to clarify the issue.