There is increasing evidence that psychosocial factors may affect health by means of biological effects and changes in behavioral health. Observational studies suggest an association between low levels of one long chain n-3 fatty acids, DHA (docosahexaenoic acid), after pregnancy and the occurrence of postpartum depression (PPD). This is an observational cohort with 4 waves of follow-up and a nested clinical trial with pregnant women residing in the city of Rio de Janeiro. The general objective is to describe the magnitude and identify factors associated to common mental disorders (CMD) during pregnancy and postpartum giving emphasis to maternal nutritional status.

Main specific objectives:

1. To evaluate the effect of CMD in the pattern of occurrence of selected maternal and child outcomes (inadequacy of gestational weight gain, postpartum weight retention, low birthweight, small for gestational weight and prematurity), considering the effect of other determinant factors, and
2. To evaluate the effectiveness of daily omega-3 doses (fish oil) in preventing PPD.

The protocol predicts CMD mapping and monitoring of nutritional status throughout pregnancy and once in postpartum. Women are interviewed in four time points:

1. First trimester: 8th and 13th (baseline),
2. Second trimester: 22nd-24th gestational weeks,
3. Third trimester: 34th-36th gestational weeks,
4. Postpartum: 30-45 days

The following information will be gathered:

1. Common mental disorders (CMD): MINI International Neuropsychiatric Interview, symptoms of depression (Edinburgh scale - EPDS), anxiety (Trait Anxiety Inventory - TAI)
2. Dietary intake (food frequency questionnaire)
3. Anthropometric measure (stature and body weight) and physical activity
4. Biochemicals: fasting glucose, lipid profile (total cholesterol, HDL-c, LDL-c), serum fatty acid composition, inflammatory markers (C-reactive protein, interleukin-6), hormones (adiponectin, insulin, leptin).

All women are followed throughout pregnancy constituting the observational cohort. In the second trimester, those women identified as being in risk for PPD [past history of depression (DSM-IV) or presenting a score of depression (Edinburgh scale) >= 9 at the baseline interview] are invited to participate in the clinical trial. These women will be randomly allocated in two groups:

Intervention 1: Fish oil: [1,8 g/dia n-3 (1,08 g EPA e 0,72 g DHA)+ vit E (0,2 mg/g) Intervention 2: Placebo comparator: soybean oil + 1% fish oil + vit E (0,2 mg/g)

The supplementation occurs from the 22nd-24th week of pregnancy for 16 weeks.](streamdown:incomplete-link)

Inclusion Criteria:

• aged 20 to 40
• up to 13 weeks of pregnancy
• free from chronic or infectious diseases (except obesity)
• residing in the study catchment area

Exclusion Criteria:

- twin pregnancies

Pregnant women attending a health care center in the city of Rio de Janeiro, Brazil