title: Pregnancy gingivitis and causal inference.
abstract: METHODS
  The PubMed and Embase databases were searched together with hand searching of the Journal of Periodontology, Journal of Periodontal Research and Journal of Clinical Periodontology. The reference lists of identified articles were also searched.
  
  
  METHODS
  Prospective cohort or cross-sectional studies assessing the effect of pregnancy on gingival inflammation evaluated by the gingival index and/or bleeding on probing were included. Study quality was assessed using the Newcastle-Ottawa scale (NOS).
  
  
  METHODS
  Study assessment and data extraction were carried out independently by two reviewers, with disputes resolved by a third reviewer. Mean values of primary and secondary outcomes were directly pooled and analysed with weighted mean differences (WMDs) and 95% confidence intervals (CIs), considering independently each study design (cohort and cross-sectional). Study specific estimates were pooled with both the fixed- and random-effect models.
  
  
  RESULTS
  Forty-four articles representing 33 studies (14 cohort and 19 cross-sectional) were included. Meta-analyses revealed a significantly lower GI in pregnant women in the first term compared with those in their second or third term of pregnancy; a lower mean GI score in post-partum women compared with women in their second [WMD = 0.143; 95% CI (0.031; 0.255); p = 0.012] or third term [WMD = 0.256; 95% CI (0.151; 0.360); p < 0.001] of pregnancy, when considering cohort studies; non-pregnant women had lower mean GI values than women in their second or third term of pregnancy. Small changes in plaque levels were reported.
  
  
  CONCLUSIONS
  The results of this systematic review confirm that gingival inflammation is significantly increased throughout pregnancy and when comparing pregnant versus post-partum or non-pregnant women, without a concomitant increase in plaque levels. However, this information should be considered with caution, due to the small number of studies included in the meta-analyses, the low quality of the included studies, differences in study design, absence of a periodontal diagnosis at baseline and performance of periodontal treatment in some cases. No conclusions could be drawn regarding secondary outcomes such as microbiological, immunological and patient-centred data, because no meta-analyses were possible for these factors. Future studies with higher quality should be designed to answer these questions.
authors.affiliation: Department of Epidemiology and Health Promotion, New York University College of Dentistry, New York, New York, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Niederman
mesh_terms: D005260:Female; D005891:Gingivitis / Q000145:classification*; D006801:Humans; D011247:Pregnancy / Q000502:physiology*