BACKGROUND
Vaginal seeding—exposure of neonates to maternal vaginal fluids—has been proposed
to improve the microbiota of infants born through cesarean delivery, but its impacts
on the infants' subsequent health outcomes remain unclear.
OBJECTIVE
This study aimed to examine the impacts of vaginal seeding on gut microbiota, growth,
and allergy risks in infants born through cesarean delivery.
STUDY DESIGN
This randomized controlled trial was conducted at Liuyang Maternal and Child Health
Care Hospital in Hunan, China. We estimated that a minimum sample size of 106 was
needed by assuming a standardized effect size of 0.6 for the primary outcomes, with
a statistical power of 80%, a 2-sided type I error of 0.05, and an expected loss to
follow-up rate of 15%. Finally, 120 singleton term pregnant women scheduled for cesarean
delivery were enrolled from November 2018 to September 2019. Infant follow-up was
completed in September 2021. The participants were randomized in a 1:1 ratio to the
vaginal seeding group (n=60; infants were swabbed immediately after birth using gauze
preincubated in maternal vagina) or the control group (n=60; routine standard care).
The first set of primary outcomes was infant body mass index and body mass index z-scores
at 6, 12, 18, and 24 months of age. The other primary outcome was the total allergy
risk score at 18 months for 20 common allergens (each scored from 0–6 points). Characteristics
of gut microbiota, overweight/obesity, and allergic diseases and symptoms were included
as secondary outcomes. The main analyses were performed according to the modified
intention-to-treat principle.
RESULTS
Of 120 infants, 117 were included in the analyses. Infant body mass index and body
mass index z-scores did not significantly differ between the 2 groups at any of the
4 time points, with the largest difference in point estimates occurring at 6 months:
the mean (standard deviation) body mass index was 17.5 (1.4) kg/m2 and 17.8 (1.8) kg/m2 in the vaginal seeding and control groups, respectively (mean difference, −0.31 kg/m2 [95% confidence interval, −0.91 to 0.28]; P=.30), and body mass index z-score was 0.2 (1.0) and 0.4 (1.1), respectively (mean
difference, −0.20 [95% confidence interval, −0.58 to 0.18]; P=.31). The median total allergy risk score was 1.5 (interquartile range, 0.0–4.0)
in the vaginal seeding group and 2.0 (interquartile range, 1.0–3.0) in the control
group (median difference, 0.00 [95% confidence interval, −1.00 to 1.00]; P=.48). For infants from the vaginal seeding group, the relative abundance of genera
Lactobacillus and Bacteroides in the gut microbiota was slightly yet nonsignificantly elevated at birth and 6 months,
and the risk of overweight/obesity was lower at 6 months (0/57 vs 6/59; relative risk,
0.03 [95% confidence interval, 0.00–0.57]; P=.03) though not at subsequent time points. Other secondary outcomes did not differ
between groups. No adverse events related to the intervention were reported.
CONCLUSION
For infants born through cesarean delivery, vaginal seeding has no significant impacts
on the gut microbiota, growth, or allergy risks during the first 2 years of life.
Keywords
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Article info
Publication history
Published online: November 02, 2022
Accepted:
October 28,
2022
Received in revised form:
October 21,
2022
Received:
July 15,
2022
Footnotes
The authors report no conflict of interest.
This work was funded by the National Natural Science Foundation of China (81701538). The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, and approval of the manuscript; or the decision to submit the manuscript for publication.
Cite this article as: Liu Y, Li H, Zhou S, et al. Effects of vaginal seeding on gut microbiota, body mass index, and allergy risks in cesarean-delivered infants: a randomized clinical trial. Am J Obstet Gynecol MFM 2022;XX:x.ex–x.ex.
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