Newnham 2009.

Methods	Study design: RCT Location: Australia Setting: Smile Study was 'single‐centre' study conducted at 7 sites in public and private antenatal clinics and offices across Perth, Western Australia Recruitment period: February 2005 and December 2007
Participants	Inclusion criteria: > 16 years of age; absence of maternal cardiac disease that would warrant the need for antibiotics for periodontal examination or treatment; not already received periodontal treatment during the current pregnancy; ≥ 20 natural teeth; single pregnancy of > 12 and < 20 weeks gestational age; did not have any known fetal anomalies or other risk factors such as hydramnios that would place the pregnancy at imminent risk of complications; able to attend regularly for periodontal treatment if required Exclusion criteria: not stated Mean age (± standard deviation (years)): Group A = 30.5 ± 5.5, Group B = 30.5 ± 5.5 (P = 0.842) Mean gestational age (± standard deviation (weeks)): Group A = 18.1 ± 2.3, Group B = 18.2 ± 2.2 (P = 0.451) History of preterm delivery (%): Group A = 13.2, Group B = 11.1 (P = 0.412) Periodontal disease: defined as periodontal probing depth ≥ 4 mm at ≥ 12 probing sites in fully erupted teeth (excluding wisdom teeth) Number randomised: n = 1087 Number evaluated: n = 1078 (attrition n = 9: loss to follow‐up n = 1, miscarriage before treatment n = 2, multiple pregnancy n = 1, withdrew consent n = 5)
Interventions	A) Antenatal periodontal treatment (n = 542): 3‐week protocol which included non‐surgical debridement of the subgingival and supragingival plaque, removal of local predisposing factors such as calculus, root planing, and adjustment of overhanging restorations. Oral hygiene instruction and motivation were provided at each visit. The advice included toothbrushing and flossing after mean and rinsing with chlorhexidine mouthwash. Local anaesthesia was used as required. Sessions were provided on 3 occasions at weekly intervals commencing around 20 weeks of gestation.Those women in whom the treatment had not been successful (19.6%) were offered a further 3‐week treatment regimen. In addition to the baseline and 28‐week examinations, examinations were also carried out at 32 and 36 weeks gestation B) Postnatal periodontal treatment (n = 540): periodontal care after birth commencing 6 weeks after delivery All women: examinations were carried out at baseline and 4 weeks after treatment (28 weeks gestational age) in both groups Treatments were conducted either by the hygienists or periodontists
Outcomes	Preterm birth; stillbirth; neonatal death; gestational age; onset of labour; birth weight; sepsis necessitating antibiotics; birth weight less than 10th percentile; sites with probing depth > 4 mm
Funding	Not stated
Notes	A sample size of 1082 women was required to detect a reduction in the preterm birth rate with 80% power. However the independent data safety monitoring committee recommended proceeding without an interim analysis after data on treatment safety and pregnancy outcomes from the trial conducted by Michalowicz 2006 were published. Primary data analysis was performed on the intention‐to‐treat principle, however, the per‐protocol analysis showed similar results as the intention‐to‐treat analysis
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomisation was conducted using computer randomisation software specifically designed to allocate each case at random with stratification for nulliparity, history of preterm birth, and current smoking"
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding of participants and caregivers not feasible
Blinding of obstetric outcome assessment (detection bias)	Low risk	All medical, nursing, perinatal pathology staff members as well as research midwives who extracted details of all medical, obstetric and neonatal outcomes from the medical records were also unaware of the treatment allocation of each woman
Incomplete outcome data (attrition bias) All outcomes	Low risk	Primary data analysis was performed on intention‐to‐treat principle, similarly low attrition rates (1.4% versus 0.2%)
Selective reporting (reporting bias)	Low risk	Birth weight and gestational age were reported as median and interquartile range
Other bias	Low risk	No apparent source of other biases