This study aims to examine whether naturally occurring bacteria in the gastrointestinal tract are associated with mood changes following childbirth, including postpartum depression. Biological samples will be collected before and after delivery to determine whether specific patterns in gut bacterial composition are linked to emotional states. The purpose of the research is to improve understanding of whether such microbial changes can help identify individuals at higher risk for postpartum depression, enabling earlier recognition and intervention.

This prospective observational pilot study is designed to explore the relationship between gut microbial diversity and depressive symptoms during the early postpartum period. Postpartum depression is one of the most frequent complications after childbirth and has a substantial impact on the physical and psychological well-being of mothers and infants. The study investigates whether differences in gut microbial composition are associated with the development of depressive symptoms following childbirth.

Pregnant individuals aged eighteen years or older planning cesarean delivery at Massachusetts General Hospital will be enrolled. Data and biological samples will be collected at two time points: within three days before delivery and within 2 days after delivery. Blood samples will be collected for measurement of inflammatory markers, and rectal swab samples will be obtained to evaluate the composition and diversity of gut microorganisms through metagenomic sequencing. A validated questionnaire assessing emotional state will be administered at the same time points, and a follow-up emotional assessment will be obtained six weeks after childbirth through the electronic medical record system.

The study examines microbial characteristics associated with the presence or absence of depressive symptoms and evaluates correlations between microbial community patterns and emotional status, aiming to identify potential microbiome-based biomarkers predictive of early onset depressive symptoms after childbirth. The research does not include drug administration, device testing, or experimental treatment. All procedures are non-invasive or minimally invasive and coincide with routine obstetric care, minimizing participant burden.

The results of this study are expected to provide preliminary evidence linking the gut microbial environment to maternal mental health. Findings may inform future strategies for early detection and prevention of postpartum depressive symptoms and support the development of personalized approaches to maternal mental wellness.

Inclusion Criteria:

• Age 18 years or older
• Gestational age at least 36 weeks, planned cesarean delivery
• Ability to understand study procedures and provide informed consent
• Voluntary agreement to participate in the study

Exclusion Criteria:

• Gastrointestinal disorders or recent antibiotic use that significantly alters gut microbiome
• Diagnosis of severe mental illness such as schizophrenia, schizoaffective disorder, bipolar disorder, or major depressive disorder with psychotic features
• Medication use during pregnancy known to influence gut microbiota, including antidepressants, antibiotics, or fish oil
• Refusal to provide rectal swab samples or inability to complete follow-up assessments

Eligible participants are cisgender women who are pregnant or postpartum. Participants must have been assigned female at birth and currently self-identify as women.

Women aged 18 years or older, with gestational age of at least 36 weeks, planning either vaginal or cesarean delivery. Individuals with serious digestive disorders, severe mental health conditions, or recent use of medications such as antibiotics or antidepressants that may affect gut bacteria are excluded.

Individual participant data will not be shared. The dataset contains sensitive clinical information from pregnant and postpartum patients at a single institution.