Table 1.

General characteristics of the included studies

Author	Year	Country	Period analysed (year)	Study design	Gestational age at dental examination	Number of subject (n)	Definition of PTB
Martinez-Martinez et al35	2016	Mexico	2013–2014	Retrospective	From the first trimester of pregnancy until 8 weeks postpartum	70	<37 weeks
Harjunmaa et al24	2015	Malawi	2011–2013	Prospective	Within 6 weeks after delivery	1024	<37 weeks
Acharya et al23	2013	India	2009	Retrospective	Within 1 day after delivery	316	<37 weeks
Vergnes et al22	2011	France	2003–2006	Retrospective	Within 2–4 days post partum	2201	<37 weeks
Ryalat et al21	2011	Jordan	2009	Prospective	Within 1 week post partum	200	<37 weeks
Durand et al17	2009	France	2005–2006	Prospective	Within 8 weeks after delivery	107	<37 weeks
Heimonen et al20	2008	Finland	2002–2004	Retrospective	Within 2 days post partum	328	<37 weeks
Mumghamba and Manji19	2007	Tanzania	NS	Retrospective	Within 40 days from delivery	373	<37 weeks
Meurman et al18	2006	Finland	1998–2000	Retrospective	From the first trimester of pregnancy	207	<37 weeks

PTB, preterm birth.