Periodontal disease, preterm birth and low birthweight

Abstract

Data sources

Medline was searched for studies from 1966 to August 2002; reference lists from those identified were also used to find other articles.

Study selection

Inclusion criteria specified observational studies that provided a risk estimate of preterm birth (PTB) or preterm low birthweight (PLBW) in babies of mothers who had periodontal diseases. Cases were defined as PTB if delivery was at <37 weeks' gestation, or as PLBW if an infant at delivery had a birthweight <2500 g and one or more of the following: gestational age <37 weeks, preterm labour or premature rupture of membrane. Studies should have defined the exposure as periodontal disease and exposure should have been used as a categorical variable in the multivariate analysis. Articles were limited to those published in English and conducted on a human study population.

Data extraction and synthesis

The strength of the relationship between periodontal disease and the risk of PTB was assessed in these studies by relative risk (RR) or odds ratio (OR). Because the risk of preterm birth was low in these studies, the relative odds provided a good approximation of RR. OR was obtained directly from each study or calculated using the available data. Before pooling the data, OR from individual studies were transformed to their natural logarithms [log(OR)] to stabilise the variances and normalise the distributions. For calculation of the pooled OR, each study was assigned a weight equalling the reciprocal of the variance of the log(OR) in that study. When the variances of log(OR)s were not reported directly in manuscripts, they were calculated. Estimates of the overall OR and the corresponding 95% confidence intervals (CI) were calculated using both fixed-effects and random-effects models. Homogeneity of effect-size across studies was tested by Q statistics. A sensitivity analysis was conducted to assess the robustness of our findings for different exclusion criteria.

Results

Five studies (three cohort and two case–control) were included. Pregnant women with periodontal disease had an overall adjusted risk of PTB that was 4.28-fold (95% CI, 2.62–6.99; P<0.005) the risk for subjects who did not have periodontal disease. The overall adjusted OR of PLBW was 5.28 (95% CI, 2.21–12.62; P<0.005), whereas the overall adjusted OR of a delivery of either PTB or PLBW was 2.30 (95% CI, 1.21–4.38; P<0.005).

Conclusions

The findings indicate that periodontal diseases in the pregnant mother significantly increase the risk of subsequent PTB or PLBW. Although it remains important to promote good oral hygiene during routine prenatal visits, there is no convincing evidence, on the basis of existing case–control and prospective studies, that treatment of periodontal disease will reduce the risk of PTB. Consequently, large, randomised, placebo-controlled, masked clinical trials are required.

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