Fish consumption in pregnancy and omega-3 status after birth are not associated with postnatal depression

Research to date suggests a relationship between fish consumption, omega-3 polyunsaturated fatty acids, and depression. However, interpretation of this research is difficult due to methodological limitations. Postpartum women provide an excellent opportunity to examine these relationships because omega-3s are transferred from mother to fetus during pregnancy and from mother to child after birth through breast milk. Hence new mothers are more likely to be depleted in omega-3s. Our aim was to determine whether prenatal fish consumption and omega-3 status after birth were associated with postnatal depression. Eighty first-time mothers were recruited; 41 who scored on or over the cut-off on one of two depression-screening instruments, and 39 in the control group. Depression was diagnosed using the Composite International Diagnostic Interview. Fish consumption was measured during pregnancy, and depression and omega-3 status were determined postnatally. Logistic regression and t-tests were used to examine relationships between fish consumption, omega-3 status, and postnatal depression, while controlling for known covariates. Prenatal fish consumption was not predictive of postnatal depression, and postnatal omega-3 status was not associated with postnatal depression. However, prenatal fish consumption did predict omega-3 status after birth. Prenatal fish consumption was measured using only a food frequency questionnaire, and no participants consumed oily fish (rich in omega-3s) regularly. There was no association between postnatal depression and either fish consumption in early pregnancy, or omega-3 status after birth. Our findings make it difficult to justify trials of omega-3 polyunsaturated fatty acids in the treatment of postnatal depression.