Increased levels of oestrogen and progesterone during pregnancy may lead to periodontal disease. The anaerobic Gram-negative bacteria classified as the "red complex" (Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola) are frequently associated with periodontal disease. Periodontopathogens produce toxins and enzymes that can enter the bloodstream and cross the placenta to harm the foetus. The response of the mother's immune system to infection by these periodontopathogens brings about the release of inflammatory mediators which may trigger preterm labour or result in low birth-weight infants. The purpose of this study was to examine the use of Perioscan as a potential screening test for mothers at risk for pre-term delivery of low birth weight infants due to periodontal disease. Subgingival plaque samples were obtained from pregnant women between the ages of 17 to 45 years attending an ante-natal clinic in the Western Cape in South Africa. Plaque samples were analyzed by the enzymatic Perioscan test for detection of the red complex in 372 sites from 66 women. Results were confirmed by polymerase chain reaction (PCR) detection of the three species of the red complex. Seventeen (25.75%) of the population group tested positive with Perioscan but only 27 (7.25%) of the 372 sites were positive. Of the 66 mothers examined, we managed to retrieve 29 records post-delivery. In all the mothers examined, Perioscan results showed an association with the indices used to diagnose periodontal disease, and could also be associated with preterm delivery of low birth-weight infants in two of the 29 maternal records recovered.