Findings

What do systematic reviews say?

7 questions · 7 findings · 1 reviews

No studies found 0 · 0%GRADE not reported 7 · 100%Very low 0 · 0%Low 0 · 0%Moderate 0 · 0%High 0 · 0%

Oral microbiome alpha diversity (Shannon index) · Pregnant women

Shannon diversity did not differ significantly between preterm and term birth (certainty not rated).

1 finding from 1 review

The role of oral dysbiosis in pregnancy complications: a systematic review and meta-analysis of preterm birth. 2026 All outcomes
Oral samples (saliva or subgingival plaque), 16S rRNA sequencing
MD 1.09 [-0.55, 2.73]
4 studies · 296 participants
GRADE not reported

Oral microbiome alpha diversity (Shannon index) · Pregnant women

In saliva samples Shannon diversity did not differ between preterm and term birth.

1 finding from 1 review

The role of oral dysbiosis in pregnancy complications: a systematic review and meta-analysis of preterm birth. 2026 All outcomes
Oral samples (saliva or subgingival plaque), 16S rRNA sequencing · Sample site: saliva
MD 0.16 [-0.22, 0.53]
2 studies · 114 participants
GRADE not reported

Oral microbiome alpha diversity (Shannon index) · Pregnant women

In V3-V4 studies Shannon diversity did not differ significantly, with very high heterogeneity.

1 finding from 1 review

The role of oral dysbiosis in pregnancy complications: a systematic review and meta-analysis of preterm birth. 2026 All outcomes
Oral samples (saliva or subgingival plaque), 16S rRNA sequencing · Amplified 16S rRNA region: V3-V4
MD 1.37 [-0.83, 3.57]
3 studies · 242 participants
GRADE not reported

Oral microbiome alpha diversity (Shannon index) · Pregnant women

In subgingival plaque Shannon diversity did not differ significantly, with very high heterogeneity.

1 finding from 1 review

The role of oral dysbiosis in pregnancy complications: a systematic review and meta-analysis of preterm birth. 2026 All outcomes
Oral samples (saliva or subgingival plaque), 16S rRNA sequencing · Sample site: subgingival plaque
MD 2.02 [-1.1, 5.15]
2 studies · 182 participants
GRADE not reported

Oral microbiome alpha diversity (Shannon index) · Pregnant women

Sensitivity analysis with Wan conversion gave a similar non-significant difference.

1 finding from 1 review

The role of oral dysbiosis in pregnancy complications: a systematic review and meta-analysis of preterm birth. 2026 All outcomes
Oral samples (saliva or subgingival plaque), 16S rRNA sequencing · Sensitivity analysis: Wan et al. conversion of summary statistics
MD 1.07 [-0.48, 2.62]
4 studies · 296 participants
GRADE not reported

Oral microbiome alpha diversity (Shannon index) · Pregnant women

In Asian studies Shannon diversity did not differ significantly between preterm and term birth.

1 finding from 1 review

The role of oral dysbiosis in pregnancy complications: a systematic review and meta-analysis of preterm birth. 2026 All outcomes
Oral samples (saliva or subgingival plaque), 16S rRNA sequencing · Geographic region: Asia
MD 0.28 [-0.00, 0.56]
3 studies · 200 participants
GRADE not reported

Oral microbiome alpha diversity (Shannon index) · Pregnant women

Sensitivity analysis with Hozo conversion gave a similar non-significant difference.

1 finding from 1 review

The role of oral dysbiosis in pregnancy complications: a systematic review and meta-analysis of preterm birth. 2026 All outcomes
Oral samples (saliva or subgingival plaque), 16S rRNA sequencing · Sensitivity analysis: Hozo et al. conversion of summary statistics
MD 0.98 [-0.43, 2.38]
4 studies · 296 participants
GRADE not reported