Ten percent of all infants currently being born in the United States are of low birth weight. This translates into one quarter of a million babies born each year weighing less than 2 500 gram (five pounds and eight ounces). Although the results of treatment aimed at rescuing these infants have been excellent, efforts to prevent preterm and low weight births have been unsuccessful with the number of underweight babies increasing by 6% from 1985 to 1993. More than 60% of infant mortality occurring among infants with no congenital defects is attributable to preterm low birth weight (PLBW). Those surviving infants are at increased risk of developing respiratory distress syndrome, anemia, jaundice, mental retardation, cerebral palsy, impaired sight and hearing, intracranial hemorrhage, malnutrition, congestive heart failure, epilepsy, attention deficit disorder, learning disabilities and impaired lung function. Most long term disability cases begin as low birth weight babies. Treatment of these PLBW infants account for 5 million days usage per annum of hospital neonatal intensive care unit facilities at a financial cost of more than $5 billion per annum. The greater picture however reveals a much heavier burden on society in terms of suffering and long term disabilities. Factors that have shown a positive association with an increased risk of PLBW include maternal age less than 17 or greater than 34 years, low socio-economic status, inadequate prenatal care, drug abuse, malnutrition, alcohol and tobacco use, diabetes, genitourinary tract infections, hypertension and multiple pregnancies. In spite of this wide range of risk factors, about 25% of PLBW cases remain unexplained. This has motivated further research into the causes of PLBW.
An association between infection and PLBW has been demonstrated by a number of studies. Maternal genito-urinary tract infection has been linked to an increased prevalence of preterm and low birth weight infants. Different studies have shown the risk to be present with clinical and sub clinical infections, that inflammation of the extraplacental membrane, a strong risk indicator, can be present without any sign of placental bacterial infection and that genitourinary tract infections without fetal-placental unit infection can be associated with low birth weight.Irrespective of the associated risk factors, common inflammatory pathways seem to mediate the development of PLBW. Researchers have however noticed that a consistent and reproducible feature of PLBW cases is an increased level of PGE2 and TNF-ý, even in the absence of clinical or subclinical infections of the genitourinary tract. This has led these researchers to conclude that most PLBW cases are probably caused by infections of unknown origin.
The first person to suggest that periodontal infections may have a detrimental effect on the unborn infant was Galloway who in 1931 postulated that periodontal disease may ³provide sufficient infectious microbial challenge² causing ³potentially harmful effects on the pregnant mother and developing fetus². A study conducted just over a decade ago at Harvard University in the Forsyth Dental Clinic found a relationship between periodontal disease and peterm births. These results were never published. Studies by Collins et al, published in 1994 and 1995 showed that experimentally induced periodontitis in pregnant hamsters can retard fetal growth. These observations prompted Offenbacher and his team of researchers to further investigate the possible link between periodontitis and PLBW in humans. They hypothesized that ³periodontal infections, which serve as resevoirs for Gram-negative anaerobic organisms, lipopolysaccharide (LPS, endotoxin), and inflammatory mediators including PGE2 and TNF-ý may pose a potential threat to the fetal-placental unit². The research team consisted of periodontists, obstetrician-gynecologists and epidemiologists. Their study and the results which were published in a supplement to the October, 1996 Journal of Periodontology represent the most current and up to date research into this potentially very important feild. Their study sample group consisted of 124 mothers, all registered patients at the University of North Carolina Prenatal Care Clinic. Information was gathered on all known risk factors as well as a number of other variables. A full mouth periodontal examination was performed on all 124 study participants. Clinical attatchment levels were measured using the cemento enamel junction as a reference point and probing depth measurements were recorded at six sites per tooth. Controls were defined as those mothers who had one or more full term, birth weight infants Ú 2500g without a history of preterm labor (PTL) or premature rupture of membranes (PROM). Cases were defined as those mothers with a history of PTL or PROM with PLBW < 2500g. Periodontal disease status was defined using full mouth, mean clinical attatchment levels for each patient. Group periodontal disease status means were thern calculated. To eliminate the effects of other risk factors and confounders, multivariate logistic regression analysis methods were used. When analysing the other demographics and characteristics of the case and control groups, no statistically significant differences were detected. Periodontal disease indicators however, showed significant differences between the case and control groups. The controls showed significantly less disease then the cases. When no analysis tecniques were used to control for other variables, periodontal disease increased the risk for PLBW by almost 6 times. After adjusting for these variables, periodontal disease increased the risk of being a PLBW case by more than 7 fold. Although the sample size of this study was relatively small, the results indicated that in this study, periodontal disease contributed to more cases of PLBW than the use of either tobacco or alcohol. It has been calculated that more than 18% of all cases of PLBW may be due to periodontal disease, making it a clinically important risk factor for PLBW.
This study has number of limitations. The study sample size is relatively small, was primarily retrospective and was conducted at only one site. Even with these limitations however, it clearly indicates an association between periodontal disease in pregnant women and PLBW. While the results of this study need to be verified with larger, prospective, multicenter studies and the existance of a causal relationship needs to be identified, they cannot be ignored. Periodontal diseases are generally preventable or treatable with good oral hygiene and regular dental office visits. The 18% of PLBW cases possibly due to periodontal diseases represents 45000 cases each year. If these cases could be prevented by providing adequate periodontal care and treatment to women of childbearing age, the savings in neonatal intensive care would be almost $1 billion. The saving in human misery and suffering would be unquantifiable. These findings mean that all pregnant women should be given a comprehensive periodontal evaluation and all active periodontal lesions should be treated and controlled.