Polymer-based Dental Filling Materials Placed During Pregnancy and Risk to the Foetus

Trine Lise Lundekvam Berge; Gunvor Bentung Lygre; Stein Atle Lie; Lars Björkman


BMC Oral Health. 2018;18(144) 

In This Article


Data from the ongoing Norwegian Mother and Child Cohort Study (MoBa), a prospective population-based cohort study conducted by the Norwegian Institute of Public Health, were used. From 1999 to the end of 2008, pregnant women in Norway were invited to MoBa through a postal invitation in connection with their first routine ultrasound examination. The participation rate was approximately 41%, and the cohort currently comprises more than 108,000 pregnancies, 114,000 children, 95,000 mothers and 75,000 fathers. Written informed consent was obtained from each participant upon recruitment.[26,27]

In the present study, data were gathered from two questionnaires that were sent to the participating women in weeks 17 and 30 of pregnancy.[28] Each woman could participate with multiple pregnancies. Only singleton births were included in the present study.

Information about white fillings placed during pregnancy was obtained from the questionnaires sent to the participants in week 30. Reported placement of white fillings was used as exposure marker. The participants reported if they had consulted a dentist during pregnancy ("Have you been to the dentist during this pregnancy? Yes/No") and if so, whether they had received white fillings ("If, yes, did the dentist put in new white fillings? Yes/No").

Women without valid information about dental treatment during pregnancy and those with missing data on birth outcomes were excluded, leaving a study population that included 90,886 pregnancies (Figure 1).

Figure 1.

Flowchart showing number of participants included in the study and the groups available for analysis

Information about gender, preterm delivery, stillbirth, malformations, birth weight and mother's age at delivery was obtained from the Medical Birth Registry of Norway (MBRN).[29] The mother's 11-digit unique personal identification number assigned to every citizen in Norway was used to link data sources. Gestational age was based on ultrasound examination in the 17th week of pregnancy.

Infants were classified as late preterm if they were born between gestational week 33 and 37, and very preterm if they were born before or during the 32nd gestational week.[30,31] Infants with a birth weight less than 2500 g at birth were classified as low-birth weight infants, and infants with a birth weight more than 4000 g were classified as high-birth weight infants.[32]

Maternal body mass index (BMI; kg/m2) was calculated from self-reported pre-pregnancy height and weight. The BMI was categorized according to the WHO classification.[33]

Information about parity, defined as the number of former births with a gestational age of 12 weeks or more, was based on data reported by the mothers in the MoBa study and from the MBRN.

Information about education, smoking habits and alcohol consumption during pregnancy was obtained from the first questionnaire completed at approximately the 17th week.

The present study is based on version 8 of the quality-assured MoBa data files. We defined dental treatment during pregnancy as follows: participants who did not consult a dentist during pregnancy (reference category); participants who consulted a dentist but had no white fillings placed; and participants who consulted a dentist and had white fillings placed (Figure 1).

Infants were defined as small for gestational age (SGA) if the weight at birth was less than the 10th percentile for gestational age and large for gestational age (LGA) if they were larger than the 90th percentile. Very small for gestational age was defined as weight below the 2.5th percentile.[34]

The odds ratio (OR) with a 95% confidence interval was calculated using logistic regression. The OR was adjusted for maternal age (≤19, 20–24, 25–29, 30–34, 35–39, 40+ years), length of education (≤12, 13–16, ≥17 years), pre-pregnancy BMI (< 18.5, 18.5–24.9, 25.0–29.9, 30.0–34.9, 35.0–39.9, ≥ 40 kg/m2), parity (first, second and more), smoking during pregnancy (never, occasionally, daily) and alcohol consumption during pregnancy (never, less than once a week, once a week, more than once a week).

Analyses were performed using IBM-SPSS (IBM Corp. Released 2016. IBM SPSS Statistics for Windows, Version 24.0, Armonk, NY, USA: IBM Corp.). p-values less than 0.05 were considered statistically significant.

The MoBa cohort study obtained a license from the Norwegian Data Inspectorate, and this research project was approved by the Regional Ethics Committee for Medical Research (REC South-East D, 2011/727).