Association between low MCV in early pregnancy and perinatal mental health in the Japan Environment and Children's Study and the possible effect of iron deficiency

Background: Postpartum anemia and iron deficiency are associated with postpartum depression. This study investigated the association between a low mean corpuscular volume (MCV) without anemia (which implies early-stage iron deficiency) in early pregnancy and perinatal mental health outcomes. Methods: The fixed data from the Japan Environment and Children's Study (JECS), a Japanese nationwide birth cohort, were used. Perinatal mental health was assessed using the Kessler 6-item psychological distress scale (K6) in mid-pregnancy and the Edinburgh Postnatal Depression Scale (EPDS) at 1- and 6-months postpartum. Results: Among the 3635 women with MCVs <85 fL in early pregnancy, the proportions of women with K6 scores >= 13 in mid-pregnancy and EPDS scores >= 9 at 1- and 6-months postpartum were 2.7 %, 12.8 %, and 9.9 %, respectively, compared with the 33,242 women with MCVs >= 85 fL at 1.9 %, 11.9 %, and 9.0 %, respectively. Multivariate logistic regression models showed that an MCV <85 in early pregnancy was associated with a K6 score >= 13 in mid-pregnancy and an EPDS score >= 9 at 1- and 6-months postpartum (adjusted odds ratio (95 % confidence interval): 1.48 (1.16-1.87), 1.14 (1.01-1.28), and 1.09 (0.95-1.24), respectively). Limitations: Low MCV values do not necessarily represent iron deficiency. Ferritin, currently the best indicator of iron deficiency, was not measured in the JECS. Conclusions: This study results suggest that a low MCV without anemia in early pregnancy is associated with a slightly increased risk of perinatal mental health deterioration.