2.2. Study Design
REGRESSION
Participants were healthy primiparous women aged 19–45 years; multiparous women, those with multiple pregnancies, those who declined to participate in the study, and those who did not submit the 1-month postpartum questionnaire were excluded.Intervention groups received omega-3 fatty acids starting in mid-pregnancy (gestational weeks 18–25) for 12 weeks. The perilla oil group received 4.0 g/day perilla oil containing 2.4 g/day ALA, while the fish oil group received 5.2 g/day sardine oil containing 1.3 g/day EPA and 0.4 g/day DHA. Perilla oil was provided by Ota Oil Co., Ltd. (Okazaki, Japan), and fish oil was provided by Nissui Corporation (Tokyo, Japan); both products were individually packaged without any labels.The mental health of participants was assessed using the Kessler Psychological Distress Scale (K6) [In the case study, data from the observational study were divided into two groups (cases with an EPDS score ≥ 9 and controls with an EPDS score < 9). Controls were divided into tertile groups according to fatty acid level, and logistic regression analysis was performed to obtain odds ratios and 95% confidence intervals.