Periodontal Disease: Could this be a Further Factor Leading to Subfertility and is There a Case for a Prepregnancy Dental Check-up ?

“…periodontal disease … [has] a negative influence on conception of the same order of magnitude as obesity.”

Periodontal disease is a severe form of gingivitis affecting the gums. It is a longstanding inflammatory and infectious disease process affecting the gums and the surrounding structures that support the teeth. With the steady progression of the inflammatory disease process, anaerobic bacteria present at the base of the gums promote local tissue destruction within the gums and supporting structures of the teeth, and a release of inflammatory chemicals locally and also into the bloodstream (cytokines), potentially affecting many organ systems. It has been known for many years that there is an association with poor oral hygiene and an individual's general health. Within the scientific literature there exists extensive publications that describe the association of poor oral hygiene with poor general health. One of the earliest reports of the negative consequences of periodontal disease upon general health was a report in 1989 of the association between gum disease and myocardial infarction [l]. Despite adjusting for confounding variables, those individuals who suffered an acute infarction were more likely to have dental problems than individuals who did not have an infarction [l]. Since this early report there are several reports that describe an association between poor oral health and cardiovascular disease, Type 2 diabetes, respiratory disease, kidney disease and poor pregnancy outcomes [2–6].

Of particular interest is the association of an adverse pregnancy outcome in the presence of periodontal disease; reports document an increase in the rate of premature delivery [7], of a growth-restricted fetus [8] and an increase in the prevalence of maternal preeclampsia [9]. Understandably, these reports led to the initiation of interventional studies on pregnant women with periodontal disease. To date, there have been several randomized controlled trials conducted in pregnancy to study the effect of treating women with periodontal disease upon pregnancy outcome. As periodontal disease is easy to treat with up to four visits to a dentist, or a dental hygienist, and with good oral hygiene, it was presumed that intervention in pregnancy would lead to an improved obstetric outcome [4]. Unfortunately, this hypothesis has not been confirmed and, indeed, the most recent review of the intervention trials in pregnancy found that there was no benefit in treating periodontal disease with regard to influencing the rate of preterm birth, low birth weight, miscarriage or stillbirths [10].

Consequently, this led our researchers to believe that treating the woman in pregnancy is perhaps ‘too late’ as the early placental environment was too established by the time the intervention commenced and hence the intervention was not commenced early enough to facilitate implantation and then lead to an improved pregnancy outcome. Through our experience in the field of IVF we are aware that the embryo-endometrial interface is crucial for successful implantation as there are many patients who have extreme difficulty in conceiving; this is believed to be due to an abnormal dialog between the embryo and the endometrium at the endometrial interface [11]. With this premise, we set out to determine how long it had taken couples attending an antenatal clinic to conceive, and to determine whether the presence of periodontal disease had led to a degree of difficulty in conceiving [12]. By collecting several other aspects of their background data we hoped to determine an influence of periodontal disease on ‘time to conceive’. This study was part of a further randomized controlled intervention trial for periodontal disease in pregnancy, the Smile Study [4]. The ‘time taken to conceive’ aspect of the study was purely an observational study, with an a priori hypothesis that periodontal disease may create an adverse environment leading to a reduced chance of conceiving.

Information on the time taken to conceive was available for almost 2000 women, and periodontal disease was documented to be present in almost a quarter of Caucasian women and over 40% of non-Caucasian women. A pregnant woman with periodontal disease took an extra 2 months on average, to conceive, a negative influence on conception of the same order of magnitude as obesity. Women without periodontal disease took on average 5 months to conceive, however, women with periodontal disease took on average just over 7 months to conceive. When the factors that are known to influence a woman's fertility were controlled for in the statistical analysis (age, BMI and smoking status), the presence of periodontal disease was still a significant negative influence on the time to conceive. Of particular interest is that the data appear to suggest that the negative influence on conception appears to be of greater impact in non-Caucasian women; the majority were Asian in this study. The explanation for this difference requires further clarification; it may be that Asian women are more susceptible to the inflammatory cytokines that are disseminated through the blood stream from the periodontal disease, and hence cover the endometrium and disrupts implantation, or it may be that the periodontal disease is just a very visible marker of inflammation that is in fact present throughout the whole body, including the endometrium, and Asian women are more susceptible to this and are hence less likely to conceive. Certainly, this study is only an observational study that raises many questions that require further investigation. However, in the meantime women trying to conceive should ensure they are in the best possible health, take their folic acid supplement and possibly consider attending the dentist. As periodontal disease is eminently treatable, at least all non-Caucasian patients attempting to conceive should be encouraged to visit a dentist prior to conceiving, and as semen parameters have been reported to improve in men treated for periodontal disease, perhaps the male partner should also attend [13], particularly as many medical conditions presenting later in life are also associated with periodontal disease [2].