Study	Reason for exclusion
Gazolla 2007	The control group consisted of women who refused to participate and were classed as the 'non‐treated' group. There was no randomisation
Geisinger 2014	Not an RCT. The study was used in generating preliminary data for another RCT
Jeffcoat 2011	Overlap with an included study (Jeffcoat 2003) and does not contain useful additional information to supplement the primary publication
Jiang 2016	The study compared antimicrobial mouthrinse with toothbrushing. Antimicrobial mouthrinse alone is not considered a periodontal treatment, however, it can be used as an adjunct to a mechanical periodontal treatment
Moreira 2014	Population consisted of a subsample of participants included in a study (Weidlich 2013) which was excluded for the wrong study population. There is lack of clarity on whether the concerns we had about the primary study were addressed in this study and obstetric outcomes were not reported
Pack 1980	Obstetric outcome not reported
Penova‐Veselinovic 2015	Participants were a subset of study population in an included study (Newnham 2009)
Thomson 1982	Obstetric outcome not reported
Weidlich 2013	Included pregnant women regardless of their periodontal status

RCT = randomised controlled trial.