Effectiveness of a family-centered behavioral and educational counselling approach to improve periodontal health of pregnant women: a randomized controlled trial

Maintaining good oral health is essential for a healthy pregnancy. Pregnancy-induced hormonal changes can affect periodontal tissues. Elevated hormone levels during pregnancy amplify the plaque-induced gingival inflammatory response, resulting in swelling and bleeding [1‐3]. The prevalence of pregnancy gingivitis has been reported to be 36–100% [4‐7]. The severity of gingival inflammation usually increases from the 16th to the 40th week of pregnancy and decreases after parturition [8, 9]. Some studies have reported increases in periodontal pocket (Poc) depth or loss of attachment (LoA) during pregnancy [3, 8, 10]. However, the differences in study design (e.g., variability of pre-existing periodontal status at baseline, lack of a non-pregnant comparison group, or a short follow-up period) make it difficult to conclude if pregnancy exacerbates periodontal damage [11].

Periodontal diseases are initiated by dental plaque, and untreated gingivitis can lead to further insult of the periodontal tissues. Periodontal disease can be prevented through oral health education (OHE). Educating pregnant women to perform effective plaque removal is imperative for the prevention and control of periodontal disease in this vulnerable group. Despite this, a recent systematic review reported that, in most of the studies, oral health promotion among pregnant women mainly involved delivering messages on infant oral health, instead of focusing on pregnant women’s oral health [12]. Some studies that targeted pregnant women only reported their oral health knowledge, oral hygiene practices, or caries status [13‐16]. Three studies reported the periodontal health outcomes, among which two studies delivered periodontal treatments to pregnant women who already had gingivitis, and the other was a short-term study (4 weeks) [17‐19]. No evidence-based conclusions could be drawn from their findings. The effectiveness of OHE for pregnant women remains a research gap.

Traditionally, there has been an emphasis on OHE for individuals. Current concepts of OHE acknowledge the importance of involvement at the individual, family, and community levels [20]. Studies have also reported the interrelationships between oral health practices and status among married couples, parents, and their children [21, 22]. Thus, delivering OHE to members in the family together (a family-centered approach) is likely to be more effective in improving the oral health of family members than delivering conventional OHE to individuals. The aim of this study was to evaluate the effectiveness of a family-centered behavioral and educational counselling approach in improving the periodontal health of women during pregnancy and 12 months postpartum, as compared with traditional OHE (distributing pamphlets alone). It was hypothesized that this approach would improve the periodontal health of pregnant women.

This study was part of a randomized controlled trial aimed to decrease the incidence of early childhood caries (ECC). A family-centered approach was used to provide behavioral and educational counselling to pregnant women and their husbands to establish self-efficacy of the new parents in their oral health self-care and oral health care for their infants so as to decrease ECC in their children at 3 years old. Comprehensive data of the pregnant women, their husbands, and their babies were collected and analyzed in the 10th-22nd gestational weeks (T₀), in the 3rd trimester of pregnancy (T₁), and when the baby was 1 year old (T₂), 2 years old (T₃), and 3 years old (T₄). The study protocol was approved by the Institutional Review Board of the University of Hong Kong (#UW 13–163) and the Research Ethics Boards at each of the participant recruitment sites, as well as registered on ClinicalTrials.​gov (#NCT02937194).

Figure 1 shows the CONSORT flowchart for the recruitment, randomization, and follow-ups of the participants. A total of 1989 pregnant women were approached, of whom 1203 met the eligibility criteria, and 589 participants with complete baseline data were recruited for this study (participation rate 49.0%). Through the random allocation, 297 and 292 participants were assigned to the test and control groups, respectively.

Table 1 summarizes the characteristics of the pregnant women who participated in the trial at baseline. Their mean age was 31.1 years (SD = 4.0), and the mean gestational age at the time of recruitment was 14.4 weeks (SD = 2.6). More than 60% of the participants had an income of HK$30,000 or more per month, which is above the average level of Hong Kong households. More than two thirds (67.1%) of the participants had received tertiary education. Less than half (40.4%) of the participants were covered by a dental care scheme. There were no statistically significant differences in the demographic characteristics, dental scheme coverage, and alcohol drinking habit between the test and control groups (p > 0.05). In contrast, there was a higher proportion of participants with a smoking habit in the control group than in the test group (p = 0.014).

At baseline, although visible plaque was detected in most (82.5%) of the study participants, only 6.6% of them had visible plaque on more than 50% of the examined tooth surfaces. Mean percentage of tooth surfaces with plaque were similar in the test and control groups at baseline (p > 0.05). Almost all (95.2%) of the participants had BOP. Over 70% of the participants had BOP in more than 50% of the periodontal probing sites. Nearly 90% of the participants were free of Poc in the sextants examined. There was no statistically significant difference between the two groups regarding the percentage of sites with BOP and the number of sextants with Poc (p > 0.05).

Table 2 shows the characteristics of participants who were followed up and those who were not. Of the 589 participants recruited, 369 (62.6%) attended both the T₁ and T₂ follow-up examinations and completed the data collection. Participants who were lost to follow-up were younger (p < 0.01). There was no statistically significant difference (p > 0.05) in other characteristics between the participants who completed the follow-ups and those who did not.

Table 3 presents the VPI score, BOP%, NPoc, and NLoA of the test and control groups and the between-group differences at the three time points. In the mixed-effect ANOVA models on VPI% and BOP% and GLMM on NPoc and NLoA, the participants’ age, gestational month, education level, monthly income, dental scheme coverage, and smoking habit were not statistically significant (all p > 0.05). These variables were removed in the final models.

At one year postpartum, more participants had healthy periodontal condition than at baseline (McNemar’s test, p < 0.001). Meanwhile, the test group had a higher proportion of individuals with healthy periodontal status than the control group one year postpartum (Chi-square test, p = 0.001) (Table 3).

At T₀, around 3% of the participants had visible plaque on more than 50% of the tooth surfaces. This proportion decreased after the intervention in the test group (3.7% at T₀; 0.5% at T₁; and 0% at T₂). In contrast, the proportion of participants in the control group with this condition increased at T₂ (2.2% at T₀; 2.2% at T₁; 5% at T₂). The mean VPI score in the test group was 0.19 at T₀, which decreased to 0.14 at T₁ and remained at this low level at T₂. In the control group, the mean VPI score slightly reduced from 0.19 at baseline to 0.16 at T₁, but increased to 0.22 at T₂. A main effect of time and intervention, as well as an interaction between time and intervention, was detected (all p < 0.05), indicating that the intervention effect differed between T₁ and T₂. The between-group difference in the change of VPI score was statistically significant (p = 0.025). Pairwise comparisons were carried out with Bonferroni adjustment. From T₀ to T₁, the decrease in mean VPI score was statistically significant in the test group (p < 0.001) but not in the control group (p > 0.05). At T₂ (12 months postpartum), the mean VPI score of the test group was similar to the corresponding T₁ values and remained significantly better than baseline (p = 0.01). However, the mean VPI score was significantly higher at T₂ compared to T₁ in the control group.

Throughout the study, the proportion of pregnant women with a severe condition of gingival bleeding (> 50% examined sites) decreased in both study groups. However, the prevalence of severe gingival bleeding was lower in the test group than in the control group at T₂ (p < 0.01). The trend of change in BOP% was similar to that of VPI. In the test group, the mean BOP% was 57% at T₀ and decreased to 46 and 35% at T₁ and T₂, respectively. The mean BOP% in the control group only slightly reduced from 58% at baseline to 52 and 46% at T₁ and T₂. A main effect of time and intervention, as well as an interaction between time and intervention, was detected (all p < 0.05), indicating that the intervention effect differed between T₁ and T₂. The test group showed a more significant decrease in BOP than the control group did.

Compared with T₀, more pregnant women had a Poc at T₁ (p < 0.01), and fewer participants had a Poc at T₂ (p < 0.001). No significant difference was found between the two study groups at all three time points (p > 0.05). In both groups, the mean NPoc increased from T₀ (around 0.2) to T₁ (about 0.3) and then decreased at T₂ (about 0.1). There were significant changes over time in both groups (p < 0.001). There was no significant intervention-time interaction, such that the intervention effect did not differ between T₁ and T₂ (p > 0.05). The finding for the NLoA was similar. There was a statistically significant change over time (p < 0.001). The mean NLoA at T₂ was significantly lower than at T₀ and T₁. There was no significant difference between the two groups over time (p > 0.05), and no interaction (p > 0.05) was observed.

The findings of this clinical trial show that the family-centered behavioral and educational counselling approach with reinforcement is more effective in improving the oral hygiene and gingival health status of pregnant women than traditional OHE by distributing pamphlets alone. Pregnancy does not necessarily lead to more severe gingivitis or periodontitis if pregnant women can be empowered to maintain good oral hygiene.

The favorable outcomes resulting from the behavioral and education counselling approach may be due to several reasons. First, even though the intervention was not developed based on a psychological theory or model, it shared some essential components of the Health Belief Model for promoting health [25]. After the behavioral and education counselling, the pregnant women were aware that they were more susceptible to periodontal disease during pregnancy (perceived susceptibility); realized that periodontal disease could have potentially severe consequences, such as preterm delivery (perceived severity); and believed that good oral hygiene practice would produce positive outcomes, such as reducing the vertical transmission of oral cariogenic bacteria to children (perceived benefits). Furthermore, the communication with the oral health educator during the reinforcements provided an opportunity to solve the problems they encountered (perceived barriers). Generally, theory-based interventions are proven to be more successful in achieving stable and permanent behavioral changes than non-theory-based interventions [26‐28]. Second, there was a detailed demonstration of oral hygiene practice adopting the “tell-show-do” approach in this study. Training on the correct toothbrushing method was delivered to the participants and focused on areas that are particularly relevant to pregnant women, such as cleaning the gingival margin of the teeth, handling nausea/vomiting when brushing teeth, and using dental floss to clean proximal surfaces. All these procedures and the feedback provided to the participants were useful to improve their capabilities to perform proper oral hygiene measures. Third, this study targeted first-time expectant mothers at their early pregnancy stage. Pregnancy, especially the first one, is a significant transition for a woman that provides an opportunity to “change” (e.g., change of nutrition-related behavior because the woman has concerns about the health of herself and her fetus) [29]. Similarly, first pregnancy may be an excellent opportunity to elicit positive changes in oral health-related behavior. Findings of a previous study suggest that pregnant women in their first trimester are more willing to participate in research projects and to receive prenatal or other health care [30]. Fourth, the intervention was family centered in that the husbands received the OHE together with the pregnant women, with reinforcement at different time points. Findings of a systematic review support that health interventions involving men can increase care seeking, improve home care practices and couple relationships, and promote women’s health [31].

This study sheds light on the impact of an oral health promotion program targeting pregnant women in a primary care setting, which has been sparse in the literature. However, this study had several limitations. First, although the participants were recruited from public prenatal care centers in different districts of Hong Kong, their socioeconomic status was higher than the average of the general population in Hong Kong. This could have led to a better response to oral health promotion. More research on interventions delivered to other populations (e.g., low-income people) is required to confirm if these findings can be generalized. Second, there was a methodological limitation in adopting the indices and the partial periodontal examination recommended by the WHO [22]. Understandably, partial mouth recordings are quicker to undertake than full mouth recordings. Although this approach may result in underestimation of the disease [32], it was essential and helpful in this study because our participants were pregnant women and the data collection was carried out during their prenatal care with limited time. This measurement approach has been recognized as being well suited for identifying individuals who are (and who continue to be) periodontally healthy [33, 34]. Thus, we can conclude that individualized behavioral and educational counselling produces promising results for maintaining good periodontal health among pregnant women.

Compared with that of the local population [35], the oral hygiene status of the participants in this study was better. Although 82.5% of them had visible plaque on the examined tooth surfaces, only about 3% of the participants had visible plaque on half or more of the surfaces. There is a potential “ceiling effect” (i.e., the reasonably good oral hygiene at baseline would make further improvement difficult). Indeed, greater efficacy could be expected if the intervention were delivered to people with poorer oral hygiene.

This study demonstrates that behavioral and educational counselling could be an effective way to maintain good periodontal health in pregnant women. A pregnant woman could receive adequate information and oral hygiene instructions from dental or non-dental health professionals (e.g., her obstetrician, midwives, nurses) and be made aware of how to improve her oral health. Psychological theory-based oral health promotion is suggested and could be incorporated into routine dental care or integrated into prenatal care. Furthermore, such an intervention should be implemented at an early stage of pregnancy, so that reinforcement sessions can be scheduled if necessary.

Providing family-centered, behavioral, and educational counselling to pregnant women at an early stage of pregnancy, and with reinforcement, can improve their oral hygiene and reduce gingival inflammation. The effect can be sustained over a more extended period than that achieved by distributing oral health leaflets alone.