Michalowicz 2006.

Methods	Study design: RCT Location: USA Setting: the Obstetrics and Periodontal Therapy (OPT) Study, a multicentre trial, was conducted in Hennepin County Medical Centre (Minnesota), the University of Kentucky, the University of Mississippi Medical Center and Harlem Hospital (New York) Recruitment period: March 2003 to June 2005
Participants	Inclusion criteria: at least 16 years of age, less than 16 weeks 6 days gestation, at least 20 natural teeth, and the presence of periodontal disease (4 or more teeth with a probing depth of at least 4 mm and a clinical attachment loss of at least 2 mm, as well as bleeding on probing at 35% or more of tooth sites) Exclusion criteria: multiple pregnancy, required antibiotic prophylaxis for periodontal procedures, medical condition that precluded elective dental treatment, had extensive tooth decay, or likely to have fewer than 20 teeth after treatment of moderate to severe caries, abscesses or other non‐periodontal pathoses. Baseline assessments were conducted between 13 weeks 0 days and 16 weeks 6 days gestation Mean age (± standard deviation (years)): Group A = 26.1 ± 5.6, Group B = 25.9 ± 5.5 (P = 0.56) Mean gestational age (± standard deviation (weeks)): Group A = 15 ± 1.3, Group B = 15 ± 1.3 (P = 0.85) History of preterm delivery (%): Group A = 12.5, Group B = 16.5 (P = 0.18) Periodontal characteristics: tooth sites with probing depth ≥ 4 mm ‐ Group A = 26.5 ± 16.6, Group B = 24.8 ± 15.9 (P = 0.13). Most women were judged to have generalised early‐moderate periodontitis Number randomised: n = 823 Number evaluated: n = 823 (for gestational age); (attrition n = 11: lost to follow‐up n = 7, withdrawal n = 2, elective abortion n = 2)
Interventions	A) Antenatal periodontal treatment; before 21 weeks gestation (n = 413): scaling and root planing until birth; removal of dental plaque and calculus from the tooth enamel and root (up to 4 treatment visits were allowed); instruction in oral hygiene, monthly tooth polishing and reinstruction in oral hygiene (actual treatment time = mean 127.7 minutes and 2.0 visits) B) Postnatal periodontal therapy (n = 410): brief oral examination at monthly follow‐ups; attended the same number of visits as the treatment in pregnancy group; periodontal therapy after birth All women: topical or systemic antimicrobials were not used; at study entry, all women were screened for periodontal disease in the obstetric clinic (assessed attachment loss, probing depth, bleeding on probing on 6 sites on each tooth, evaluation of dental plaque and calculus on selected teeth). Women were referred to a dentist for treatment of teeth that were abscessed, fractured or likely to become symptomatic during the study. Full‐mouth assessments were repeated at 21 to 24 weeks gestation and again at 29 to 32 weeks gestation Over half the women (59%) were judged to need essential dental care (239 (61%) in the treatment group and 244 (57%) in the control group) and 73% of these women (74% in the treatment group and 71% in the control group) completed the recommended treatment. Control women with progressive periodontitis at 6 or more sites were offered full‐mouth scaling and root planing. Treatment group participants with progressive disease at 6 or more tooth sites were referred to a consulting periodontist and could receive a second course of full‐mouth scaling and root planing and/or systemic antibiotics, or subgingival irrigation with antimicrobial solutions No information on the expertise of the dental professional who administered intervention
Outcomes	Periodontitis progression (increase in clinical attachment loss from baseline of at least 3 mm); birth weight; gestational age at birth; labour induced before 37 weeks (due to hypertension, diabetes or pre‐eclampsia); spontaneous abortion (loss before 20 weeks); stillbirth (loss from 20 weeks to 36 weeks and 6 days); maternal death; bacteria from subgingival plaque sampled at 29 to 32 weeks gestation; child neurodevelopment
Funding	Funding from the National Institute of Dental and Craniofacial Research
Notes	Calculations showed that 405 patients per group would be required to show statistical significance with a power of 90% for gestational age
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "randomization, stratified by center with the use of permuted randomized blocks of 2 and 4, was made by a telephone call to the coordinating center"
Allocation concealment (selection bias)	Low risk	Quote: "randomization, stratified by center with the use of permuted randomized blocks of 2 and 4, was made by a telephone call to the coordinating center"
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not feasible to blind intervention for participants and some personnel
Blinding of obstetric outcome assessment (detection bias)	Low risk	Quote: "(obstetrical) examiners and nurses were not aware of the study group assignments"
Incomplete outcome data (attrition bias) All outcomes	Low risk	The numbers evaluated varied between outcomes, however, attrition rates were similarly low and balanced across groups. 395/413 women in the treatment in pregnancy group received treatment (18 women failed to attend treatment visits or withdrew); 413 women in the treatment group and 410 women in the control group received monthly follow‐ups and 407 and 405 women respectively, were included in the gestational age analysis (99% of women overall). During pregnancy, 6 women in the treatment group withdrew (4 were lost to follow‐up, 1 withdrew consent and 1 had an elective abortion). In the control group 5 women withdrew (3 were lost to follow‐up, 1 withdrew consent and 1 had an elective abortion)
Selective reporting (reporting bias)	Low risk	All expected outcomes were reported
Other bias	Low risk	No indication of other sources of bias