Researchers studied how bacteria in mothers’ milk and babies’ stomachs change during the first two months after birth. They looked at mothers who practiced traditional postpartum rest and compared those who did a relaxation exercise with those who didn’t. The study found that babies’ gut bacteria shifted naturally over time, with helpful bacteria increasing and potentially harmful ones decreasing. Interestingly, mothers who did relaxation exercises had different bacteria in their breast milk compared to the control group. This suggests that a mother’s stress level might actually affect the bacteria she passes to her baby through breast milk, which could be important for baby’s health.

The Quick Take

  • What they studied: Whether a mother’s stress level affects the tiny bacteria in her breast milk and her baby’s stomach, and how these bacteria naturally change during the first 8 weeks after birth.
  • Who participated: Chinese mothers who gave birth between 34-37 weeks (slightly early) and their babies who were exclusively breastfed. The mothers practiced traditional postpartum confinement (a cultural practice of rest after birth). Some mothers did relaxation exercises while others didn’t.
  • Key finding: Babies’ gut bacteria changed naturally over the first 8 weeks, with good bacteria (Bifidobacterium) increasing and potentially problematic bacteria decreasing. Mothers who did relaxation exercises had different bacteria in their breast milk compared to mothers who didn’t, suggesting stress reduction may influence what bacteria babies receive.
  • What it means for you: If you’re a new mother, managing stress through relaxation techniques may help shape the healthy bacteria you pass to your baby through breast milk. However, this is early research, and more studies are needed before making specific recommendations. Talk to your doctor about stress management during the postpartum period.

The Research Details

This was a randomized controlled trial, which is one of the strongest types of research studies. Researchers divided mothers into two groups: one group did relaxation exercises while the other group (control group) did not. They collected samples from three places: the mother’s stool, the mother’s breast milk, and the baby’s stool. They collected these samples at two time points: around 1 week after birth and again at 8 weeks. They used a special DNA test to identify and count all the different bacteria in each sample.

The researchers specifically looked at mothers who gave birth slightly early (between 34-37 weeks) and whose babies were exclusively breastfed. All mothers practiced traditional Chinese postpartum confinement, which is a cultural practice involving rest and specific dietary practices after birth. This study design allowed researchers to see how bacteria naturally change over time and whether the relaxation intervention made a difference.

This research approach is important because it looks at bacteria in three connected places (mother’s gut, breast milk, and baby’s gut) rather than just one. This helps researchers understand how bacteria might travel from mother to baby. By comparing a relaxation group to a control group, researchers can see whether stress reduction actually causes changes in bacteria, not just whether changes happen naturally. The longitudinal design (following people over time) is also valuable because it shows how bacteria evolve during this critical early period of a baby’s life.

This study has several strengths: it’s a randomized controlled trial (a high-quality study design), it followed mothers and babies over time, and it used modern DNA sequencing to identify bacteria accurately. However, the sample size was not reported in the abstract, which makes it harder to assess how reliable the findings are. The study was conducted in a specific population (Chinese mothers practicing traditional confinement), so results may not apply equally to all populations. This is a secondary analysis, meaning researchers used data from a larger study for a new purpose, which is acceptable but requires careful interpretation.

What the Results Show

The study found that the overall diversity of bacteria (how many different types are present) stayed relatively stable in all three sample types—mother’s stool, breast milk, and baby’s stool. However, the types of bacteria present did change over the 8-week period.

In breast milk, the bacteria composition shifted between week 1 and week 8, with this change being statistically significant (p = 0.039). Interestingly, this shift was mainly driven by the control group (mothers who didn’t do relaxation exercises), suggesting that the relaxation intervention may have helped keep breast milk bacteria more stable.

In babies’ guts, there were clear positive changes: helpful bacteria called Bifidobacterium increased over time, while potentially problematic bacteria (Staphylococcus and Enterobacteriaceae) decreased. These changes are generally considered beneficial for infant health. The mother’s gut bacteria remained stable throughout the study, suggesting that pregnancy and postpartum changes don’t dramatically alter a mother’s own gut bacteria.

A particularly interesting finding was that mothers in the relaxation intervention group showed a significant reduction in Staphylococcus bacteria in their breast milk compared to the control group. Staphylococcus can sometimes cause infections, so reducing it in breast milk could potentially be beneficial. This specific finding suggests that maternal stress reduction may have a direct effect on the bacteria mothers pass to their babies through breast milk. The stability of maternal gut bacteria despite the postpartum period suggests that the mother’s own digestive system is relatively resilient during this time.

Previous research has shown that breast milk contains bacteria and that these bacteria can influence baby’s gut health. This study adds to that knowledge by showing that maternal stress may be one factor that influences which bacteria are present in breast milk. The finding that babies’ beneficial bacteria increase naturally over the first weeks of life aligns with other research showing that exclusively breastfed babies develop different, generally healthier bacterial communities compared to formula-fed babies. However, the specific link between maternal stress reduction and breast milk bacteria composition is relatively new and needs confirmation from additional studies.

Several important limitations should be considered: First, the exact number of mothers and babies studied wasn’t reported in the abstract, making it difficult to assess how reliable the findings are. Second, this study was conducted in a specific cultural context (Chinese mothers practicing traditional postpartum confinement), so the results may not apply equally to mothers in other cultures or situations. Third, while the study shows that stress reduction is associated with changes in breast milk bacteria, it doesn’t prove that stress reduction causes these changes or that these changes actually improve baby’s health. Fourth, the study only followed babies for 8 weeks, so we don’t know if these early bacterial changes have long-term health effects. Finally, the study didn’t measure whether the relaxation intervention actually reduced stress, so we can’t be certain that stress reduction was the mechanism behind the observed changes.

The Bottom Line

Based on this research, managing stress during the postpartum period through relaxation techniques appears to be a reasonable approach that may influence the bacteria in breast milk. However, this is preliminary evidence, and more research is needed. Current confidence level: MODERATE for stress reduction being beneficial, LOW for specific health outcomes. General recommendations: New mothers should focus on stress management through evidence-based techniques like relaxation exercises, meditation, or counseling if needed. Continue exclusive breastfeeding as planned, as it clearly supports healthy bacterial development in babies. Discuss postpartum stress management with your healthcare provider.

This research is most relevant to: pregnant women planning to breastfeed, new mothers in the first 8 weeks postpartum, healthcare providers supporting postpartum mothers, and researchers studying infant microbiome development. This research is less directly applicable to: mothers who cannot breastfeed, mothers in very different cultural contexts than the study population, or mothers whose babies are born significantly earlier or later than 34-37 weeks. Anyone with concerns about their baby’s health or their own postpartum stress should consult their healthcare provider.

If a mother were to use relaxation techniques during pregnancy and early postpartum, changes in breast milk bacteria would likely occur within the first 1-2 weeks postpartum based on this study. However, the long-term health benefits for the baby are unknown and would require additional research to determine. Don’t expect immediate, obvious changes—these are microscopic bacteria that require laboratory testing to detect.

Want to Apply This Research?

  • Track daily stress levels using a simple 1-10 scale and note which relaxation techniques were used (deep breathing, meditation, gentle exercise, etc.). Record this alongside breastfeeding duration and any infant digestive symptoms (gas, constipation, diarrhea) to look for patterns over the first 8 weeks postpartum.
  • Implement a daily 10-15 minute relaxation practice during the postpartum period. This could include guided breathing exercises, meditation apps, gentle stretching, or progressive muscle relaxation. Log the practice in the app each day and note your stress level before and after.
  • Create a weekly summary view showing stress levels, relaxation practice consistency, and any changes in infant digestive health or feeding patterns. This helps identify correlations between maternal stress management and infant wellbeing over the critical first 8 weeks postpartum.

This research is preliminary and should not replace professional medical advice. The study was conducted in a specific population and may not apply to all mothers and babies. While the findings suggest that stress reduction may influence breast milk bacteria, this does not prove it improves baby’s health outcomes. Always consult with your pediatrician or healthcare provider regarding your baby’s health, feeding, digestion, or any concerns about postpartum stress or mental health. If you experience postpartum depression or anxiety, seek professional help immediately—these conditions require proper medical treatment.