History of Periodontal Treatment and Risk for Intrauterine Growth Restriction (IUGR)

Cande V. Ananth; Howard F. Andrews; Panos N. Papapanou; Angela M. Ward; Emilie Bruzelius; Mary Lee Conicella; David A. Albert


BMC Oral Health. 2018;18(161) 

In This Article


Study Design and Data Sources

This retrospective cohort study examined insurance records of women concurrently enrolled in medical and dental insurance plans through Aetna Inc., a nationwide, private health insurer. Aetna's data warehouse holds claim information on members for a four-year period. We therefore restricted the analysis to women that delivered a singleton live-birth between January 2010 and December 2011, and then included claims data for those birth events up to one year before gestation and up to one year after the birth event. We chose to restrict the study to singleton gestations, since the etiology and risk factors for IUGR vary between singleton and multiple births. The study cohort was restricted to women who had both medical and dental insurance, who were between 13 and 50 years of age at the time of delivery, and for whom zip code level data and other covariates were available. The analytic sample included 32,168 women.

Using data from 212,427 dental claim records for the period January 2009 through December 2012, procedures performed before, during and after pregnancy were identified and classified using the Code on Dental Procedures and Nomenclature Current Dental Terminology (CDT) 2009–10 edition for procedures occurring before 2011, and the CDT 2011/2012 edition for procedures from 2011 onwards. Maternal oral treatment type included periodontal treatment, prophylaxis, other dental treatment, or no oral treatment of any kind during the study period. Periodontal treatment was provided by general dentists and periodontists. Oral prophylaxis procedures can be provided by dentists or dental hygienists, however in the United States most oral prophylaxis procedures are provided by dental hygienists. Periodontal treatment included surgical and non-surgical codes (Additional file 1: Table S1). Because the insurance database did not include indicators of conception, the date of conception was estimated from the date of birth. For analytic purposes, each dental treatment category was considered in relation to the time period in which it occurred: pre-conception, during gestation, or after birth. The insurance dataset contained diagnosis codes and treatment codes for medical care, however it was limited to treatment codes for dental services. In the United States, dentists are only required to provide treatment codes for reimbursement via a dental claim. Given that periodontal disease is a chronic condition, periodontal treatment occurring after delivery was considered to indicate that periodontitis was present and untreated during pregnancy.

Using data extracted from 2,622,764 medical claims records, for the period January 2009 through December 2012, presence of IUGR was assumed if one or more International Classification of Diseases (ICD) 9th revision codes indicating slow fetal growth and fetal malnutrition (764.x), or poor fetal growth affecting management of mother (656.5x) had been used. Fetal growth restriction was defined as an IUGR diagnosis within 14 days of delivery; thus, in this study, the term IUGR refers to growth restriction defined accordingly. In each record, both primary and secondary claims were searched. Multiple births were identified and eliminated from the analytic file using supplementary delivery codes V27.2 to V27.9.

Maternal income, race and ethnicity were not available in the insurance database. We therefore imputed these characteristics based on the zip code of residence for each woman at the time of insurance enrollment, and the 2010 United States Census zip code level data for these variables. We identified complications of pregnancy using ICD-9 codes (Additional file 1: Table S2). Because not all women had dental coverage for the entire study period, months of enrollment for each woman was included as a covariate. The sample included women from all 50 states, the District of Columbia, and Puerto Rico.

Statistical Analysis

The risk of IUGR was associated with types of dental and periodontal treatment, as previously defined. We fit logistic regression models from which we derived odds ratios (OR) and 95% confidence intervals (CI) to assess the magnitude of the effect. In these models, we adjusted for potential confounding factors including pregnancy complications, maternal age at delivery, primiparity, zip code level income, race, and ethnicity; the models were also adjusted for duration of continuous dental coverage during the study period. Annual income was analyzed in quintiles, and categorized in US dollars as ≤28,125; 28,126 to 33,500; 33,501 to 39,283, 39,284 to 48,831; and ≥ 48,832. To assess non-linear effects of maternal age on the odds of incident IUGR, we included a quadratic term for age in the regression models.

To test for parity-related effect modification, a two-way interaction term between periodontal treatment and primiparity was included in the logistic regression model. Since the Wald-type chi-square test for the interaction term was significant (P < 0.01), we present the results of models stratified by parity.

To determine whether risk of IUGR increases with severity of periodontitis, we examined the rate of IUGR in relation to the number and type of periodontal treatment procedures, and compared women who received surgical as opposed to non-surgical periodontal treatment.

Sensitivity Analysis

Since the association between periodontal treatment and IUGR is likely affected by unmeasured confounding, we undertook a sensitivity analysis to evaluate the extent to which unmeasured confounding may have impacted the associations.[11] This sensitivity analysis was based on the following assumptions: (i) the prevalence rates of the unmeasured confounder among pregnancies with and without IUGR were 3% and 6%, respectively; and (ii) the odds ratio of IUGR comparing the presence versus absence of unmeasured confounding was allowed to vary between 0.1 (protective) to 1.0 in 0.1 increments, and 2.0 (increased risk) to 10 in 1.0 increments. The evaluation of the impact of unmeasured confounding was based on fairly conservative assumptions.