Offenbacher et al. were the first to report a link in humans between poor maternal periodontal health and composite adverse pregnancy outcome of pre-term low birth weight (PLBW). They reported that women with periodontal disease were much more likely than periodontally healthy women to experience pre-term and low birth weight infants (OR=7.5 for all PLBW cases; OR=7.9 for primiparous PLBW cases). Pro-inflammatory mediators generated within the diseased periodontal tissue may affect the maternal-foetal unit. When present in the amniotic fluid, chronic high levels of cytokines and prostaglandins may lead to intra-uterine growth restriction (IUGR), spontaneous pre-term labour, premature rupture of membranes, and pre-term birth. Several studies report associations of adverse pregnancy outcome with higher gingival crevicular fluid levels of PGE2 and IL-1β and elevated amniotic fluid concentrations of PGE2, IL-1β and IL-8 Dörtbudak. It is possible that IL-6 produced in inflamed periodontal tissues can affect the foetal membranes and cause pre-term uterine contractions. There is evidence that the gingival crevicular fluid levels of IL-6 are higher in gingivitis and periodontitis compared with healthy controls.