Research Article: Perinatal death and exposure to dental amalgam fillings during pregnancy in the population-based MoBa cohort

Date Published: December 7, 2018

Publisher: Public Library of Science

Author(s): Lars Björkman, Gunvor B. Lygre, Kjell Haug, Rolv Skjærven, Rogelio Cruz-Martinez.

http://doi.org/10.1371/journal.pone.0208803

Abstract

The aim was to gain knowledge regarding the risk of perinatal death related to exposure to dental amalgam fillings in the mother.

Population-based observational cohort study.

The Norwegian Mother and Child Cohort Study, a Norwegian birth cohort of children born in 1999–2008 conducted by the Norwegian Institute of Public Health.

72,038 pregnant women with data on the number of teeth filled with dental amalgam.

Data on perinatal death (stillbirth ≥ 22 weeks plus early neonatal death 0–7 days after birth) were obtained from the Medical Birth Registry of Norway.

The absolute risk of perinatal death ranged from 0.20% in women with no amalgam-filled teeth to 0.67% in women with 13 or more teeth filled with amalgam. Analyses including the number of teeth filled with amalgam as a continuous variable indicated an increased risk of perinatal death by increasing number of teeth filled with dental amalgam (crude OR 1.065, 95% CI 1.034 to 1.098, p<0.001). After adjustment for potential confounders (mothers' age, education, body mass index, parity, smoking during pregnancy, alcohol consumption during pregnancy) included as categorical variables, there was still an increased risk for perinatal death associated with increasing number of teeth filled with amalgam (ORadj 1.041, 95% CI 1.008 to 1.076, p = 0.015). By an increased exposure from 0 to 16 teeth filled with amalgam, the model predicted an almost doubled odds ratio (ORadj 1.915, 95% CI 1.12 to 3.28). In groups with 1 to 12 teeth filled with amalgam the adjusted odds ratios were slightly, but not significantly, increased. The group with the highest exposure (participants with 13 or more teeth filled with amalgam) had an adjusted OR of 2.34 (95% CI 1.27 to 4.32; p = 0.007). The current findings suggest that the risk of perinatal death could increase in a dose-dependent way based on the mother’s number of teeth filled with dental amalgam. However, we cannot exclude that the relatively modest odds ratios could be a result of residual confounding. Additional studies on the relationship between exposure to dental amalgam fillings during pregnancy and perinatal death are warranted.

Partial Text

Perinatal death of a child is associated with major emotional and social effects on the mother [1], and epidemiological information regarding maternal lifestyle exposure associated with stillbirth is a defined research priority. Maternal smoking, overweight and obesity are potentially modifiable established risk factors for stillbirth in high-income countries, but a large proportion of stillbirths is unexplained [2]. In high-income countries, a decrease in stillbirths has been observed over the past decades, but there is still considerable variation. Data indicate that further reductions in stillbirth are possible in high-income countries [2].

The analyses included 72,038 singleton pregnancies (62,832 mothers participating with one to four pregnancies) with data on the number of teeth filled with amalgam. Descriptive data by amalgam group (0, 1–4, 5–8, 9–12, and 13+ teeth filled with amalgam) are given in Table 1. Of the included pregnancies, 208 (0.3%) ended with perinatal death (Table 2). The absolute risk for perinatal death ranged from 0.20% in participants with no amalgam-filled teeth to 0.67% in participants with 13 or more teeth filled with amalgam. Analyses including number of teeth filled with amalgam as a continuous variable indicated an increased risk of perinatal death for higher numbers of teeth filled with dental amalgam (crude OR 1.065, 95% CI 1.034 to 1.098, p<0.001, Table 3). After adjustment for potential confounders (mothers' age, education, body mass index, parity, smoking during pregnancy, alcohol consumption during pregnancy), the adjusted OR was 1.041 (95% CI 1.008 to 1.076, p = 0.015, Table 3), indicating an increased risk for perinatal death associated with higher numbers of teeth filled with amalgam. The OR was almost doubled (OR 1.915, 95% CI 1.12 to 3.28) for participants with 16 teeth filled with amalgam compared with participants without amalgam fillings (Fig 1). There was no major effect from clustering of pregnancies within mothers.   Source: http://doi.org/10.1371/journal.pone.0208803