Treating periodontal infections during pregnancy is unlikely to reduce the risk of preterm birth.

A trial of dental hygiene treatment was conducted among pregnant women in Pennsylvania. The initial phase was the development of standard criteria to determine if periodontal disease was present. This involved measurement of gingival pocket depth and connective tissue attachment to teeth.

In the second phase, 322 pregnant women with periodontal disease were given oral hygiene instruction and free supplies of floss, brushes and toothpaste. Half were randomised to have dental scaling and root planing as well.

No significant difference in the incidence of preterm births was seen between the two groups; 52.4% in the control group and 45.6% in the intervention group.

The third phase of the study looked at those women who had the scaling and root planing. All received treatment before 20 weeks gestation and an assessment of the success or otherwise of treatment 20 weeks later. Success equated to improvement in periodontal disease criteria or being no worse. A total of 49 successful and 111 unsuccessful cases were identified. The numbers of preterm deliveries were 4 and 69 respectively, indicating a strong association between periodontal disease progression in pregnancy and preterm delivery. There was a significant relationship between successful periodontal treatment and full-term birth, adjusted odds ratio 6.02 (95% CI: 2.57-14.03, p<0.00001).

Of course association does not imply causation. More assiduous efforts at dental hygiene through pregnancy may simply be a marker of other factors more directly related to term delivery.

Pregnancy predisposes women to gum problems and encouraging treatment has preventative benefits. But can treating mild dental infection actually reduce pregnancy complications and in particular preterm delivery? Reducing periodontal anaerobic bacterial foci it is postulated might be protective. Other studies to date have been contradictory.

However, a meta-analysis published in the BMJ of 11 trials, covering 6,558 women, found no reduction in preterm birth or low birthweight from scaling and root planing during pregnancy.

The authors of the meta-analysis conclude that: ‘updated evidence does not encourage the use of scaling and root planing as an efficient method of reducing the rate of preterm birth or improving perinatal outcomes.'

Dr Chris Barclay